DE102014218971A1 - Methods and systems for moisture and PCV flow detection via an exhaust gas sensor - Google Patents

Abstract

Methods and systems for estimating PCV flow to an engine based on the output of an exhaust gas oxygen sensor are provided. During DFSO conditions, a sensor reference voltage is modulated initially at an open throttle and then at a closed throttle. Both leakage of PCV flow past the piston valves in an aging engine and an estimate of ambient humidity are derived based on sensor outputs during open and closed intake throttle modulation.

Description

The present application generally relates to the detection of ambient humidity via an exhaust gas sensor disposed in an exhaust system of an internal combustion engine.

During the conditions without fueling the engine, in which at least an inlet valve and an exhaust valve work, such. For example, during fuel cutoff (DFSO), ambient air may flow through the engine cylinders and into the exhaust system. In some examples, an exhaust gas sensor may be used to determine ambient humidity during non-fueling conditions of the engine. Due to the closing of the intake throttle during the fuel-unconditioned condition of the engine, a large intake manifold vacuum is created that can draw in the crankcase ventilation (PCV) hydrocarbons. Even if a PCV port is closed during DFSO, the negative pressure per se may be sufficiently strong to suck in PCV hydrocarbons through the piston rings. The aspirated PCV flow may be exacerbated in an aging engine due to the leakage of the PCV gases past the piston rings and the valves. The ingested hydrocarbons affect the output of the exhaust gas sensor and can confound the humidity measurements. In particular, the effect of the hydrocarbons results in a sensor output that overestimates the ambient humidity.

The inventors here have recognized the above problem and have developed an approach to at least partially treat it. Thus, a method for an engine system including an exhaust gas sensor is disclosed. In one example, during non-fueling conditions of the engine when at least one intake valve and one exhaust valve are operating, the method includes modulating a reference voltage of an exhaust gas sensor with an open and closed intake throttle; and indicating engine wear based on the PCV flow, wherein the crankcase ventilation (PCV) flow is based on the outputs of the sensor during modulating. The method may further include generating an indication of ambient humidity based on an output of the exhaust gas sensor when the intake throttle is closed and the estimated PCV flow. In this way, a more accurate estimate of ambient humidity can be obtained and the PCV flow can be better estimated and the PCV flow better accommodated.

During selected fuel cutoff (DFSO) events, an engine controller may modulate the reference voltage of an inlet oxygen sensor to estimate both ambient humidity and PCV flow. The controller may first modulate the reference voltage with the intake throttle open and re-modulate the voltage with the intake throttle closed. With the intake throttle open, the manifold pressure is increased and the PCV flow to the inlet is reduced. During such conditions, a change in the pumping current displayed on the sensor during modulating indicates ambient humidity. With the inlet throttle closed, the manifold pressure is reduced and the PCV flow to the inlet is increased. During such conditions, during modulating, a change in the pumping current displayed on the sensor indicates both the ambient humidity and an effect of the PCV hydrocarbons. By comparing the change in pumping currents estimated with the intake throttle open and closed, an amount of PCV flow received during closed throttle conditions in the engine may be identified. In addition, if the PCV port was closed during modulating, the PCV flow may be compared to a threshold to identify PCV flow leakage past the piston rings, where an indication of engine aging and component wear may be signaled. The ambient humidity may also be modified based on the PCV flow experienced. The more reliable estimate of the ambient humidity without the effects of the hydrocarbons from the PCV can then be used to adjust the operating parameters of the engine without suffering engine control problems.

In this way, the effect of PCV on moisture measurement by an exhaust gas oxygen sensor is reduced. By selectively opening the intake throttle during a DFSO when moisture measurement is required, the intake manifold vacuum is reduced, which reduces the amount of PCV hydrocarbons being drawn into the engine. In addition, even if any PCV hydrocarbons are taken in, the increased airflow reduces the PCV concentration sensed by the exhaust gas sensor during DFSO. As such, the ambient humidity can be determined more accurately and reliably.

It should be understood that the summary above is provided to provide a selection of concepts in a simplified form which are further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is clearly defined by the claims which follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that eliminate all disadvantages noted above or in any part of this disclosure.

The figures show:

1 FIG. 10 shows an example embodiment of a combustion chamber in an engine system including an exhaust system and an exhaust gas recirculation system. FIG.

2 shows a schematic diagram of an exemplary exhaust gas sensor.

3 FIG. 10 is a flowchart illustrating a routine for determining a measurement mode of an exhaust gas sensor. FIG.

4 FIG. 10 is a flowchart illustrating a routine for determining ambient humidity based on an exhaust gas sensor. FIG.

5 Figure 9 is a graph illustrating the effect of PCV hydrocarbons on moisture estimation.

6 FIG. 10 is a flowchart illustrating a routine for adjusting engine operating parameters based on ambient humidity generated by an exhaust gas sensor.

7 shows the exemplary effect of PCV flow on moisture determination.

The following description relates to methods and systems for an engine system having an exhaust gas oxygen sensor, such as an exhaust gas sensor. B. the engine system after 1 and the exhaust gas oxygen sensor 2 , During selected non-fueling conditions of the engine, the exhaust gas oxygen sensor may be used for moisture estimation and / or PCV flow estimation. A controller of the engine system may be configured with code to execute a control routine, such as a control routine. B. the routines after the 3 - 4 to modulate a reference voltage applied to the exhaust gas oxygen sensor during non-fueling conditions of the engine at an open intake throttle and then again with the intake throttle closed. By comparing the outputs of the sensor during modulating, the controller can learn both ambient humidity and PCV flow rate. The in-service may be based on the linear relationship between the exhaust water content and a pumping current output by the sensor ( 6 ). The controller may then set one or more engine operating parameters based on the humidity experienced and the PCV flow experienced ( 5 ). Additionally, based on the sensed PCV flow, the controller may identify the degradation of the engine components resulting in PCV leakage. An exemplary setting is with respect to 7 shown.

1 FIG. 12 is a schematic diagram illustrating a cylinder of a multi-cylinder engine. FIG 10 in an engine system 100 shows, which may be included in a drive system of a motor vehicle. The engine 10 can be at least partially controlled by a control system that has a controller 12 contains, and by an input from an operator 132 of the vehicle via an input device 130 be controlled. In this example, the input device contains 130 an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. A combustion chamber (ie a cylinder) 30 the engine 10 can combustion chamber walls 32 contain, in which a piston 36 is positioned. The piston 36 can be connected to a crankshaft 40 be coupled, so that a reciprocating motion of the piston is converted into a rotational movement of the crankshaft. The crankshaft 40 may be coupled via an intermediate gear system to at least one drive wheel of a vehicle. Further, a starter motor via a flywheel to the crankshaft 40 be coupled to a starting operation of the engine 10 to enable.

The combustion chamber 30 can intake air through an inlet channel 42 from an intake manifold 44 receive and can the combustion gases through an exhaust duct 48 Drain. The intake manifold 44 and the outlet channel 48 can optionally have an inlet valve 52 or an outlet valve 54 with the combustion chamber 30 keep in touch. In some embodiments, the combustion chamber 30 include two or more intake valves and / or two or more exhaust valves.

In this example, the inlet valve 52 and the exhaust valve 54 by cam actuation via respective cam actuation systems 51 and 53 be controlled. Each of the cam actuation systems 51 and 53 may include one or more cams, and may include a cam curve switching (CPS) system and / or a variable cam timing (VCT) system and / or a variable rate system Valve Timing Control (VVT) and / or a variable valve lift (VVL) system used by the controller 12 can be operated to vary the valve operation. The positions of the inlet valve 52 and the exhaust valve 54 can through the position sensors 55 respectively. 57 be determined. In alternative embodiments, the inlet valve 52 and / or the exhaust valve 54 be controlled by an electric valve actuation. The cylinder 30 can z. Alternatively, an intake valve controlled by an electric valve actuation and an exhaust valve controlled via a cam operation including CPS and / or VCT systems may be included.

It is shown that a fuel injector 66 directly to the combustion chamber 30 is coupled to the fuel proportional to the pulse width of a signal FPW, via an electronic driver 68 from the controller 12 is received, to inject directly into it. In this way, the fuel injector 66 that's what's ready as a direct injection of the fuel into the combustion chamber 30 is known. The fuel injector may, for. B. on the side of the combustion chamber or in the upper part of the combustion chamber (as shown). The fuel may flow through a fuel delivery system (not shown) including a fuel tank, a fuel pump, and a fuel rail 66 be supplied. In some embodiments, the combustion chamber 30 alternatively or additionally, include a fuel injector configured in a configuration that provides what is referred to as the port injection of the fuel into the intake port upstream of the combustion chamber 30 is known in the intake manifold 44 is arranged.

The inlet channel 42 can a throttle 62 Contain a throttle plate 64 having. In this particular example, the position of the throttle plate 64 through the controller 12 Be changed via a signal that is an electric motor or an actuator operating in the throttle 62 is provided, a configuration commonly referred to as an electronic throttle control (ETC). That way the throttle can work 62 be operated to that of the combustion chamber 30 to vary intake air provided under the other engine cylinders. The position of the throttle plate 64 can the controller 12 be provided by a throttle position signal TP. The inlet channel 42 can be an air mass flow sensor 120 and a manifold air pressure sensor 122 included to the respective signals MAF and MAP the controller 12 provide.

It is shown that an exhaust gas sensor 126 upstream of an exhaust gas purification device 70 to the outlet channel 48 is coupled. The sensor 126 may be any suitable sensor to provide an indication of the air / fuel ratio of the exhaust gases, such as. B. a linear oxygen sensor or UEGO (a universal or wide-range exhaust gas oxygen), a two-state oxygen sensor or EGO, a HEGO (a heated EGO), a NO _x , HC or CO sensor. It is shown that the emission control device 70 downstream of the exhaust gas sensor 126 along the outlet channel 48 is arranged. The device 70 it may be a three way catalyst (TWC), a _NOx trap, various other emission control devices or combinations thereof. In some embodiments, during operation of the engine 10 the exhaust gas purification device 70 be periodically reset by operating at least one cylinder of the engine with a specific air / fuel ratio.

Further, in the disclosed embodiments, an exhaust gas recirculation (EGR) system may be provided. 140 a target portion of the exhaust gas from the exhaust passage 48 via an EGR channel 142 to the intake manifold 44 conduct. An EGR amount corresponding to the intake manifold 44 can be provided by the controller 12 via an EGR valve 144 be varied. Furthermore, an EGR sensor 146 within the EGR channel 142 may be arranged, wherein it can provide an indication of the pressure and / or the temperature and / or the concentration of the constituents of the exhaust gas. Under some conditions, the EGR system may 140 may be used to control the temperature of the air-fuel mixture within the combustion chamber, and thus provide a method of controlling ignition timing during some combustion modes. Further, during some conditions, a portion of the combustion gases may be controlled by controlling the timing of the exhaust valve, such as exhaust valve timing. For example, controlling a variable valve timing mechanism may be held or captured in the combustion chamber.

The controller 12 is in 1 shown as a microcomputer, which is a microprocessor unit 102 , the input / output ports 104 , an electronic storage medium for executable programs and calibration values, which in this particular example is a read-only memory chip 106 shown is a read-write memory 108 , a hold 110 and a data bus. The controller 12 For example, in addition to those signals previously discussed, various signals may be sent to the engine 10 Receive coupled sensors, including the measurement of the inducted mass air flow (MAF) from the mass air flow sensor 120 ; one Engine coolant temperature (ECT) from a temperature sensor 112 which is connected to a cooling sleeve 114 is coupled; a Profile Ignition Pickup (PIP) signal from a Hall effect sensor 118 (or another type) attached to the crankshaft 40 is coupled; a throttle position (TP) from a throttle position sensor; and a manifold absolute pressure signal MAP from the sensor 122 , The engine speed signal, RPM, can be controlled by the controller 12 be generated from the signal PIP. The manifold pressure signal MAP from a manifold pressure sensor may be used to provide an indication of the vacuum or pressure in the intake manifold. It is stated that various combinations of the above sensors may be used, such as: B. a MAF sensor without a MAP sensor or vice versa. During stoichiometric operation, the MAP sensor may indicate an indication of engine torque. Further, this sensor may provide an estimate of the charge introduced into the cylinder (including the air) along with the detected engine speed. In one example, the sensor 118 Also used as an engine speed sensor, each time the crankshaft rotates, it generates a predetermined number of equally spaced pulses.

The read-only memory 106 The storage medium may be programmed with computer readable data representing nonvolatile instructions issued by the processor 102 are executable to perform both the methods described below and other variants that are foreseen but not specifically listed.

As described above, shows 1 only one cylinder of a multi-cylinder engine, wherein each cylinder similarly may include its own set of intake / exhaust valves, a fuel injector, a spark plug, and so forth.

2 shows a schematic view of an exemplary embodiment of an exhaust gas sensor, such. B. a UEGO sensor 200 which is configured to measure a concentration of oxygen (O ₂ ) in an exhaust gas stream. The sensor 200 can z. As the exhaust gas sensor 126 work as above re 1 has been described. The sensor 200 includes multiple layers of one or more ceramic materials arranged in a stacked configuration. In the embodiment according to 2 There are five ceramic layers as the layers 201 . 202 . 203 . 204 and 205 shown. These layers contain one or more layers of a solid electrolyte that can conduct ionic oxygen. Examples of suitable solid electrolytes include, but are not limited to, zirconia-based materials. Furthermore, in some embodiments, such as. B. those in 2 shown is a heater 207 be arranged in thermal communication with the layers to increase the ionic conductivity of the layers. While the illustrated UEGO sensor 200 is formed of five ceramic layers, it is recognized that the UEGO sensor may contain other suitable numbers of ceramic layers.

The layer 202 Contains a material or materials that have a diffusion path 210 produce. The diffusion path 210 is configured to transfer exhaust gases via diffusion into a first internal cavity 222 initiate. The diffusion path 210 may be configured to allow one or more components of the exhaust gases including, but not limited to, a desired analyte (eg, O ₂ ) at a more restrictive rate into the interior cavity 222 to diffuse, as the analyte through a pair of pump electrodes 212 and 214 can be pumped in or out. In this way, a stoichiometric level of O ₂ in the first internal cavity 222 to be obtained.

The sensor 200 also includes a second internal cavity 224 within the shift 204 coming from the first inner cavity 222 through the layer 203 is disconnected. The second inner cavity 224 is configured to maintain a constant oxygen partial pressure equivalent to a stoichiometric condition, one in the second internal cavity 224 existing oxygen level is z. B. equal to that which the exhaust gas would have if the air-fuel ratio was stoichiometric. The oxygen concentration in the second internal cavity 224 is kept constant by the pumping current I _cp . Here is the second inner cavity 224 be referred to as a reference cell.

A pair of scanning electrodes 216 and 218 is with the first inner cavity 222 and the reference cell 224 arranged in connection. The scanning electrode pair 216 and 218 detects a concentration gradient extending between the first internal cavity 222 and the reference cell 224 due to an oxygen concentration in the exhaust gas that is higher or lower than the stoichiometric level. A high oxygen concentration can, for. B. caused by a lean exhaust gas mixture, while a low oxygen concentration can be caused by a rich mixture.

The pair of pumping electrodes 212 and 214 is in connection with the inner cavity 222 and is configured to receive a selected gas constituent (eg, O ₂ ) from the interior cavity 222 through the layer 201 and from the sensor 200 to pump electrochemically. Alternatively, the pair of pumping electrodes 212 and 214 configured be to put a selected gas through the layer 201 and in the inner cavity 222 to pump electrochemically. Here can the pump electrode pair 212 and 214 be referred to as an O ₂ pump cell.

The electrodes 212 . 214 . 216 and 218 can be made of various suitable materials. In some embodiments, the electrodes 212 . 214 . 216 and 218 be at least partially made of a material that catalyzes the dissociation of molecular oxygen. Examples of such materials include, but are not limited to, electrodes containing platinum and / or gold.

The process of electrochemical pumping of oxygen from or into the internal cavity 222 includes the application of an electrical current I _p across the pump electrode pair 212 and 214 , The pumping current I _p applied to the O ₂ pumping cell pumps oxygen into or out of the first internal cavity 222 to maintain a stoichiometric level of oxygen in the void pumping cell. The pumping current I _p is proportional to the concentration of oxygen in the exhaust gas. Consequently, a lean mixture causes oxygen from the internal cavity 222 Pumping while a rich mixture causes the oxygen in the inner cavity 222 is pumped.

A control system (which in 2 not shown) generates a pump voltage signal V _p as a function of the intensity of the pump current I _p required to reach a stoichiometric level within the first internal cavity 222 maintain.

The exhaust gas oxygen sensor as such is at a first, lower reference voltage (Vs), such. B. 450 mV, operated. When the voltage to a second, higher reference voltage, such. For example, if the temperature is changed above 800 mV (eg 1080 mV), the sensor dissociates the water in the exhaust gas and measures the additional oxygen from the water. This phenomenon can then be used to advantage to measure ambient humidity. When operating specifically at the lower reference voltage (450 mV), the pumping current is proportional to the oxygen concentration [O ₂ ]. When the sensor is then operated at the higher reference voltage (1080 mV), additional oxygen is released due to dissociation of the water (H ₂ O -> H ₂ + 1 / 2O ₂ ), the change in the pump current corresponding to the excess oxygen, is measured to determine the water concentration [H ₂ O]. As in the graph 600 to 6 is shown, the pumping current (Ip, along the y-axis) varies linearly with the water concentration ([H ₂ O], along the x-axis). The relationship can be defined by the following equation: Ip = 0.114 [H ₂ O] mA - 0.00011mA.

An adaptation by linear regression of the graphic representation 6 provides a regression coefficient R ² of 0.999. At the higher reference voltage of 1080 mV, the sensor resolution is on the order of 2 μA.

It should be appreciated that the UEGO sensor described herein is merely one example embodiment of a UEGO sensor and that other embodiments of UEGO sensors may include additional and / or alternative features and / or designs.

However, the exhaust gas oxygen sensor is affected by the presence of hydrocarbons in the exhaust air. Specifically, the exhaust gas hydrocarbons at the sensor may be oxidized into carbon dioxide and water, causing the sensing element of the exhaust gas oxygen sensor to indicate a lower amount of oxygen than is actually present. As such, this causes the ambient humidity estimated based on the output of the UEGO to be incorrect (eg, the ambient humidity is overestimated). While this problem can be dealt with by measuring the water content in the air during DFSO conditions when the engine is not fueled, the measurement may still be affected by the presence of the hydrocarbons taken up by the PCV port. These include the crankcase gases and the crankcase ventilation hydrocarbons (PCV hydrocarbons). Even if the PCV port is blocked (eg by closing a PCV valve), PCV hydrocarbons can be absorbed by the piston rings. While z. For example, if an intake throttle is open during the DFSO condition, the intake MAP may be low enough to aspirate PCV hydrocarbons. The problem can be exacerbated with aging engines where there may be additional PCV leakage due to wear of the piston rings and valves. The increased PCV increases the engine's oil consumption, the loss of peak torque and affects the output of the humidity sensor. To control PCV flow and identify any major engine component wear, it is necessary to monitor the PCV flow as such. However, no robust mechanism is currently available to determine PCV flow and / or determine PCV content.

As for the 3 - 5 the inventors have recognized here that the effect of the PCV hydrocarbons by opening the intake throttle during the DFSO Events while the humidity is estimated by the exhaust gas oxygen sensor can be minimized or even eliminated. By opening the intake throttle, the manifold pressure can be increased. This reduces delta pressure above the PCV port, thereby reducing the amount of PCV flow drawn into the intake manifold. The increased MAP also increases the pressure in the cylinder, which reduces the hydrocarbon (or oil) flow through the piston rings into the cylinder air. Further, the increased MAP increases the airflow during the DFSO event, which reduces the oil or hydrocarbon vapor concentration. The combined effect reduces the overall impact of the PCV flow on the measurement of oxygen from the dissociated water of the ambient humidity of the exhaust gas sensor.

In addition, while estimating ambient humidity, the same exhaust gas sensor may be advantageously used to estimate the PCV flow of the engine and to identify the wear of the engine components resulting in PCV flow leakage. Specifically, the reference voltage of the exhaust gas oxygen sensor may be modulated during DFSO open intake valve and then intake valve closed events, where the delta Ip may be compared at both conditions to estimate the amount of PCV flow.

Then, engine operating parameters may be adjusted based on the more accurate estimate of ambient humidity and PCV flow.

The 3 - 5 show flowcharts illustrating routines for an exhaust gas sensor and an engine system, respectively. In the 3 shown routine determines z. Based on the fueling conditions of the engine, whether the sensor should be operated to measure the exhaust gas oxygen concentration or the ambient humidity or the PCV flow. In the 4 The routine shown determines ambient humidity and the amount of PCV flow based on the exhaust gas sensor 200 that concerning 2 has been described. 5 FIG. 12 shows a routine for adjusting the operating parameters of the engine based on ambient humidity and PCV flow in excess of those in FIG 3 shown routine can be determined. In addition, the routine allows for 5 in that the wear of engine components is identified based on the amount of PCV flow relative to a threshold.

In 3 is a flowchart that is a routine 300 for controlling an exhaust gas sensor, such. B. the exhaust gas oxygen sensor, the above with respect 2 has been described and which is positioned as in 1 is shown, shown, shown. The operating mode of the sensor is controlled based at least on the fueling conditions of the engine. Specifically, the routine determines whether the engine system is operating under fuel-leaning conditions, setting a sensing mode of the sensor accordingly. During conditions without Kraftstoffbeaufschlagung the sensor z. B. operated in a mode to determine the ambient humidity and / or the PCV flow, while operated during the conditions with fueling the sensor in a mode to measure the exhaust gas oxygen concentration to the air-fuel ratio determine.

at 302 the routine 300 to 3 The operating conditions of the engine are determined. As non-limiting examples, the engine operating conditions may include the actual / desired EGR, ignition, air-fuel ratio, engine speed, atmospheric pressure, engine coolant temperature, and so on.

Once the operating conditions have been determined, at 304 the routine 300 determines if the engine is under fuel-free conditions. The fuel-less conditions include the engine operating conditions where the fuel supply is interrupted but the engine continues to rotate and at least one intake valve and one exhaust valve are operating; consequently, air flows through one or more of the cylinders, but no fuel is injected into the cylinders. Under the non-fueling conditions, no combustion is performed whereby the ambient air may move from the intake passage through the cylinder to the exhaust passage. In this way, a sensor, such. B. an exhaust gas oxygen sensor, ambient air received on the measurements, such. As the detection of ambient humidity can be performed.

The conditions without Kraftstoffbeaufschlagung z. As the fuel cut-off (DFSO) included. The DFSO is in response to the operator pedal (eg, in response to a driver's pedal release and where the vehicle accelerates greater than a threshold amount). The DAFOE conditions may occur repeatedly during a drive cycle, thus providing numerous indications of ambient humidity throughout the drive cycle, such as driving conditions. During each DFSO event. As such, the overall efficiency of the engine may be maintained during the driving cycles in which ambient humidity fluctuates. The Ambient moisture can z. B. due to a change in altitude or temperature or when the vehicle enters fog or rain / fog or rain leaves, fluctuate.

If it is determined that the engine is not operating under the non-fueling conditions, e.g. For example, when fuel is injected into one or more cylinders of the engine, the routine passes 300 to 308 , at 308 For example, the exhaust gas sensor is operated as an air-fuel ratio sensor. In this mode of operation, the sensor z. B. operated as a lambda sensor. As a lambda sensor, the output voltage may determine whether the exhaust air-fuel ratio is lean or rich. Alternatively, the sensor may operate as a universal exhaust gas oxygen (UEGO) sensor, wherein an air-fuel ratio (eg, a degree of deviation from a stoichiometric ratio) may be obtained from the pumping current of the pumping cell of the sensor.

at 310 the routine 300 the air-fuel ratio (FAR) is controlled in response to the exhaust gas oxygen sensor. Thus, a desired FAR of the exhaust gases may be maintained based on the feedback from the sensor during engine fueling conditions. If z. For example, if a desired air-fuel ratio is the stoichiometric ratio and the sensor determines that the exhaust gas is lean (ie, the exhaust gas includes excess oxygen and the FAR is less than stoichiometric), additional fuel may be injected during subsequent fueling of the engine become. As another example, if a desired air-fuel ratio is the stoichiometric ratio and the sensor determines that the exhaust gas is rich (ie, the exhaust gas includes excess fuel and the FAR is greater than stoichiometric), then fuel injection may be reported during subsequent operation Fueling the engine are reduced.

On the other hand, if it is determined that the engine is under the non-fueling conditions, the routine will increase 306 further, wherein the sensor is operated to determine the ambient humidity and / or the PCV flow to the engine. The ambient humidity and PCV flow may be determined based on the sensor output, as discussed below 4 will be described in more detail. A reference voltage of the sensor may, for. B. between a minimum voltage at which oxygen is detected, and a voltage at which water molecules can be dissociated, so that the ambient humidity can be determined modulated. The process can be repeated with both the intake throttle open (where the PCV flow is reduced or eliminated) and the intake throttle closed (where the PCV flow is enabled), and the difference in sensor outputs at the two throttle conditions can be used to determine the Derive PCV flow. It should be appreciated that the ambient humidity as determined (which is referred to below 4 described), which is absolute ambient humidity. In addition, the relative humidity can be obtained by further comprising a temperature detection device, such. As a temperature sensor is used.

4 shows a flowchart that is a routine 400 for determining ambient humidity and PCV flow e.g. B. via an exhaust gas sensor, such. B. the oxygen sensor, the above with respect 2 has been described and which is positioned as in 1 shown is illustrated.

at 401 The routine includes closing a PCV opening. If z. For example, if a PCV valve coupling the engine crankcase to the intake manifold is present, the valve may be closed. Closing the valve reduces the uptake of PCV hydrocarbons, minimizing their effect on the output of the exhaust gas oxygen sensor.

at 402 The routine includes opening an intake throttle to increase manifold pressure (MAP), thereby reducing intake of PCV flow past the piston rings. The opening of the intake throttle includes, in one example, the full opening of the intake throttle. In another example, the intake throttle may be opened by at least 15 degrees. As previously discussed, opening the intake throttle will reduce the impact of the PCV flow (such as any PCV flow exiting past the piston rings). This is due to the increase in MAP causing a drop in delta pressure over the PCV port, which reduces the amount of PCV flow into the intake manifold. The increased MAP also increases the cylinder pressure which reduces the flow of PCV hydrocarbons through the piston rings into the cylinder air. Finally, the increased MAP also increases the total airflow during the DFSO event, which reduces the effective concentration of hydrocarbon vapors.

at 404 For example, when the intake throttle valve is open, the routine includes modulating a reference voltage of the exhaust gas sensor. Here, the exhaust gas sensor is an exhaust gas oxygen sensor. Modulating the reference voltage includes switching the reference voltage between a first, lower one Reference voltage and a second, higher reference voltage. Specifically, the sensor is included 406 operated at the lower reference voltage, wherein a first output by the sensor (IP1) pumping current is displayed. Then at 408 the reference voltage is increased until the sensor operates at the higher reference voltage and a second pump current output by the sensor (IP2) is displayed. As a non-limiting example, the first voltage may be 450 mV and the second voltage may be 1080 mV. With the inlet throttle open at 450 mV, the first pumping current (IP1 = Ip_450_np_pcv) can indicate an amount of oxygen in the exhaust gas. At 1080 mV, water molecules can be dissociated so that the second pumping current indicates the amount of oxygen in the exhaust gas plus an amount of oxygen from the dissociated water molecules (IP2 = Ip_1080_no_pcv). The first voltage can z. Example, be a voltage at which a concentration of oxygen in the exhaust gas can be determined, while the second voltage may be a voltage at which water molecules can be dissociated.

At 1080 mV, carbon dioxide (CO ₂ ) molecules can be dissociated as such in addition to the water molecules. However, during conditions when the intake throttle is open and the engine is not fueled, carbon dioxide may not be generated from the oxidation of the hydrocarbons (eg, the fuel or oil) and thereby may not affect the moisture estimate.

at 408 The routine includes determining a change in pumping current (delta-Ip) during modulation. at 410 An average change in pumping current can be determined. During a DFSO event with the throttle open, for example: For example, the modulating may be performed for a duration, wherein a change in the pumping current may be learned at each modulation. Then the values learned can be averaged. As such, because this delta Ip is based on the sensor output displayed with the inlet throttle open, the delta Ip represents the change in pumping current only from the ambient humidity (without any contribution from the PCV flow). Consequently, this first change in pumping current can be stored as Delta_ip_no_pcv and can be considered: Delta_ip_no_pcv = Ip_1080_no_pcv - Ip_450_no_pcv = IP2 - IP1 be learned.

By modulating the reference voltage and determining an average change in the pump current, z. For example, the effect of a changing air-fuel ratio at the beginning of a fuel cut-off period when residual spread gases may be present in the exhaust gas may be canceled. As such, an indication of the ambient humidity can be generated relatively quickly after the fuel injection has been suspended, even if the exhaust gas is not free of residual combustion gases.

at 412 For example, the ambient humidity may be estimated based on the first change in pumping current (Delta_ip_no_pcv). Because the pumping current output by the sensor at the second voltage (dissociated at the water molecules) specifically indicates the amount of oxygen in the exhaust gas plus an amount of oxygen from the dissociated water molecules, while that through the sensor at the first voltage (at which no water molecules The first pumping current indicative of the amount of oxygen in the exhaust gas indicates the first change in pumping current (the difference between the first pumping current and the second open-throttle valve pumping current) estimated during the fuel-free condition of the engine, wherein at least an inlet valve and an outlet valve operate to ambient humidity.

It will be appreciated that in some examples, modulating the reference voltage for determining ambient humidity may be based on the duration of the fuel off. The routine may, for. B. optionally determine a duration since stopping the fuel. If the duration since fuel cutoff is less than a threshold duration, the reference voltage of the sensor is modulated between the first voltage and the second voltage to determine the ambient humidity. If the duration since fuel cutoff is greater than the threshold duration, the reference voltage will not be modulated. In some examples, the duration since the fuel has been shut off may be a period of time since the fuel has been shut off. In other examples, the duration since the fuel has been shut off may be a number of engine cycles since the fuel has been shut off. As such, the threshold duration may be a period of time until the exhaust gas is substantially free of hydrocarbons from combustion in the engine. The residual gases from one or more previous combustion cycles may, for. B. remain in the exhaust gas during a plurality of cycles after the fuel has been turned off, wherein the gas that is discharged from the chamber during a period after the fuel injection has been stopped may contain more than the ambient air. Further, the period of time in which the fuel is shut off may vary. An operator of the vehicle may, for. B. release an accelerator pedal and to idle, resulting in a long DFSO time. In some situations, the period of time the fuel is shut off (eg, the period from fuel cut to fuel restart) may not be long enough for the ambient air in the exhaust system to reach an equilibrium state. An operator of the vehicle may, for. B. pedaling shortly after releasing the accelerator pedal, causing the DFSO to stop soon after it starts. In such a situation, the controller may modulate the reference voltage as in 404 has been discussed. In comparison, if the duration since fuel cutoff is greater than the threshold duration, the reference voltage is increased to a threshold voltage but not modulated. The threshold voltage may be a voltage at which a desired molecule is dissociated, such as. B. the second, higher reference voltage of 1080 mV. In another example, only during the moisture estimation (not the estimation of the PCV flow) can the second, higher reference voltage used be 950 mV or another voltage at which water molecules can be dissociated.

Back at the routine 400 includes the routine at 414 after estimating ambient humidity, closing the intake throttle to reduce manifold pressure (MAP) and thereby increase the intake of PCV flow past the piston rings into the intake manifold of the engine. The closing of the intake throttle includes the complete closing of the intake throttle. As such, closing the intake throttle will increase the impact of the PCV flow.

It will be added next 416 With the inlet throttle closed, the reference voltage of the exhaust gas oxygen sensor is modulated. As for re 404 Modulating the reference voltage includes switching the reference voltage between the first, lower reference voltage (eg, 450 mV) and the second, higher reference voltage (eg, 1080 mV). Specifically, at 418 the sensor is operated at the lower reference voltage and a first pump current output by the sensor (IP1 '= Ip_450_w_pcv) is displayed. Then at 419 increases the reference voltage, the sensor is operated at the higher reference voltage and a second pump current output by the sensor (IP2 '= Ip_1080_w_pcv) is displayed. With closed inlet throttle at 450 mV, the pumping current z. B. indicate an amount of oxygen in the exhaust gas. With the throttle closed at 1080 mV, the carbon dioxide molecules (CO ₂ molecules) can be dissociated in addition to the water molecules. Specifically, during conditions when the intake throttle is closed and the engine is not fueled, the carbon dioxide may be generated from the oxidation of the hydrocarbons (eg, the fuel or oil) and therefore may affect the humidity estimate. Thus, at 1080 mV, water molecules and carbon dioxide molecules can be dissociated such that the pumping current indicates the amount of oxygen in the exhaust gas plus an amount of oxygen from the dissociated water molecules plus an amount of oxygen from the dissociated carbon dioxide (CO ₂ ) molecules. The CO ₂ is generated from the PCV hydrocarbons which react with oxygen at the sensing element of the exhaust gas oxygen sensor to produce CO ₂ and water.

at 420 The routine includes determining a change in pumping current (delta-Ip) during modulation. at 422 An average change in pumping current can be determined. During the DFSO event when the intake throttle is closed, e.g. For example, the modulating may be performed for a duration, wherein a change in the pumping current may be learned at each modulation. Then the values learned can be averaged. As such, because this delta Ip is based on the sensor output displayed with the inlet throttle closed, the delta Ip represents the change in pumping current from ambient humidity with an additional contribution from the PCV flow. Consequently, this second change in pumping current can be stored as Delta_ip_w_pcv and as: Delta_ip_w_pcv = Ip_1080_w_pcv - Ip_450_w_pcv = IP2 '- IP1' be learned.

at 424 For example, the PCV flow may be estimated based on the outputs of the exhaust gas oxygen sensor during open and closed intake throttle modulation. Specifically, a PCV flow rate (under closed throttle conditions) is determined based on a difference (eg, as a function of a difference) between the first change in pumping current output by the sensor during open-port throttle modulation (FIG. Delta_ip_no_pcv, as at 408 is determined) and the second change in the pumping current output by the sensor during modulating with the inlet throttle closed (Delta_ip_w_pcv, as in FIG 422 determined). In other words, the PCV flow can be calculated according to the equation: PCV_flow = f (Delta_ip_w_pcv - Delta_ip_no_pcv), with f = function of,
be determined.

As for re 5 2, an engine controller may then indicate engine degradation (eg, engine component wear) based on the estimated PCV flow. Further, the controller may determine an operating parameter of the engine based on the indication of ambient humidity (as at 412 learned) and the estimated PCV flow (as with 424 learned).

It will be appreciated that in some embodiments, the indication of ambient humidity may be generated based on the output of the open throttle sensor and also based on the estimated PCV flow.

In this way, the controller may first modulate the reference voltage of the exhaust gas sensor between the first, lower voltage and the second, higher open throttle voltage, and then close the intake throttle and again modulate the reference voltage between the first and second closed throttle voltage. The controller may then estimate ambient humidity based on the outputs of the sensor during open intake throttle modulation, while estimating the PCV flow based on the outputs of the sensor during open throttle modulation with respect to the outputs of the sensor during closed intake throttle modulation ,

As described in detail above, an exhaust gas sensor may be operated in various modes in which the pumping voltage or the pumping current of the pumping cell is monitored. As such, the sensor may be used to determine both the absolute ambient humidity of the air surrounding the vehicle, the PCV flow through the engine, and the exhaust gas air-fuel ratio. Subsequent to the detection of ambient humidity, PCV flow and air-fuel ratio, multiple engine operating parameters may be set for optimal engine performance, as will be explained in detail below. These parameters include, but are not limited to, an amount of exhaust gas recirculation (EGR), ignition, air-fuel ratio, fuel injection, and valve timing. In one embodiment, one or more of these operating parameters (eg, EGR, ignition, air-fuel ratio, fuel injection, valve timing, etc.) are not adjusted during modulating the reference voltage of the exhaust gas sensor.

5 shows a flowchart that is a routine 500 for setting z. B. the operating parameters of the engine based on an ambient humidity generated by an exhaust gas sensor, such. B. the ambient humidity that is generated as with respect 4 has been described. The operating parameters of the engine may also be adjusted based on the estimated PCV flow. An increase in the water concentration of the air surrounding the vehicle can, for. B. dilute a charge mixture, which is supplied to a combustion chamber of the engine. If one or more operating parameters are not adjusted in response to the increase in humidity, engine power and fuel economy may decrease and emissions may increase; consequently, the overall efficiency of the engine may be reduced. As another example, the presence of the PCV flow into the engine may increase the fuel content of the air entering the cylinders. If fuel injection into the cylinders is not adjusted in response to the increase in fuel, engine power and fuel economy may decrease and emissions may increase; consequently, the overall efficiency of the engine may be reduced.

at 502 The operating conditions of the engine are determined. The operating conditions of the engine may include, but are not limited to, the EGR, the ignition, and the air-fuel ratio, which may be affected by the fluctuations in the concentration of water in the ambient air.

Once the operating conditions have been determined, the routine will increase 504 Continue, taking the estimated ambient humidity during the routine 4 is retrieved. Once the ambient humidity has been retrieved, the routine will start 506 Next, where is the amount of PCV flow that occurs during the routine 4 is retrieved. at 508 For example, after retrieving both the PCV flow and the ambient humidity estimate, one or more operating parameters are set based on the estimated ambient humidity and the PCV flow. Such operating parameters may include, but are not limited to, an amount of EGR, spark timing, and air-fuel ratio. As has been described above, it is desirable in internal combustion engines to increase the operating parameters of the engine, such as the engine. As the ignition plan to optimize the engine performance. In addition, engine control functions that affect the ambient humidity are adjusted. These can be z. B. both the Spark compensation (eg spark compensation factors) including condensation models (eg, the condensation modeling coefficients) as well as humidity sensor diagnostics (eg, thresholds for the OBD routines of the humidity sensor). The operating parameters of the engine influenced by the PCV flow may be e.g. B. containing the fuel injection quantities. In some embodiments, only one parameter may be adjusted in response to moisture and PCV flow. In other embodiments, any combination or sub-combination of these operating parameters may be adjusted in response to the measured fluctuations in ambient humidity.

In an exemplary embodiment, an amount of EGR may be adjusted based on the measured ambient humidity. Under one condition, for. For example, the water concentration in the air surrounding the vehicle due to a weather condition such. Fog, have increased; consequently, during the non-fueling conditions of the engine, higher humidity is detected by the exhaust gas sensor. In response to the measurement of increased humidity, during the subsequent operation of fueling the engine, the EGR flow into at least one combustion chamber may be reduced. As a result, the engine efficiency can be maintained.

In response to a fluctuation of the absolute ambient humidity, the EGR flow in at least one combustion chamber may be increased or decreased. As such, the EGR flow may be increased or decreased in only one combustion chamber, in some combustion chambers, or in all combustion chambers. Additionally, the magnitude of the change in EGR flow may be the same for all cylinders, or may vary the magnitude of the change in EGR flow based on the specific operating conditions of each cylinder per cylinder.

In another embodiment, the ignition may be adjusted in response to ambient humidity. Under at least one condition can z. For example, the ignition in one or more cylinders may be advanced during the subsequent operation of fueling the engine in response to a higher humidity reading. The spark timing can z. For example, to reduce knock under conditions of low humidity (eg, retard from peak torque timing). When an increase in humidity is detected by the exhaust gas sensor, the ignition may be advanced to maintain engine power and operate closer to or at peak torque ignition.

In addition, the ignition may be retarded in response to a decrease in ambient humidity. A decrease in the ambient humidity of a higher humidity can, for. B. cause knocking. If the decrease in moisture by the exhaust gas sensor during the conditions without fuel injection, such. As the DFSO is detected, the ignition during the subsequent operation of the fueling of the engine can be retarded and the knocking can be reduced.

It should be noted that the spark may be advanced or retarded during the subsequent operation of fueling the engine in one or more cylinders. Further, the magnitude of the change in ignition may be the same for all cylinders, or one or more cylinders may have varying amounts of spark advance or retard.

In yet another exemplary embodiment, the exhaust gas air-fuel ratio may be adjusted during the subsequent operation of fueling the engine in response to the measured ambient humidity. An engine can z. B. work with a lean air-fuel ratio, which is optimized for the low humidity. In the case of an increase in humidity, the mixture may be diluted, resulting in engine misfire. However, if the increase in humidity by the exhaust gas sensor is detected during the non-fueling conditions, the air-fuel ratio may be adjusted so that the engine having a leaner air-fuel ratio that is less lean during the subsequent operation of the engine Fueling works. Likewise, an air-fuel ratio may be adjusted in response to a measured decrease in ambient humidity to be leaner in air-fuel ratio during the subsequent fueling operation of the engine. In this way, the conditions such. For example, an engine misfire can be reduced while the capability fluctuations are reduced.

In some examples, an engine may operate with a stoichiometric air-fuel ratio or a rich air-fuel ratio. As such, the air-fuel ratio may be independent of ambient humidity with the measured fluctuations of the ambient humidity Moisture can not lead to an adjustment of the air-fuel ratio.

In yet another embodiment, the fuel injection may be adjusted in response to the PCV flow, wherein the fuel injection during subsequent fueling conditions of the engine (ie, engine fueling conditions after the DFSO event where the humidity and PCV Flow) has decreased as the PCV flow is increased.

From 506 The routine may also be too 510 - 512 go to identify the wear of the engine components based on the estimated PCV flow. Specifically, at 510 the estimated PCV flow is compared to a threshold. The threshold may be based on the levels of PCV flow measured during known engine wear. Alternatively, the threshold may be based on a change in the air-fuel ratio modeled based on the PCV flow. at 512 The routine includes specifying engine wear based on the estimated PCV flow that is higher than the threshold. Specifying the wear of the engine may include indicating the wear of the engine components, such as the engine components. As the piston rings or valves included. As such, if the estimated PCV flow is not greater than the threshold, no wear can be determined and the routine may end.

In some embodiments, a diagnostic code may be set in response to the indication of wear. Optionally, one or more operating parameters of the engine may be adjusted based on the indication. A lot of the EGR can z. B. based on the estimated PCV flow, which is higher than the threshold can be reduced.

In one example, during a first unconditioned fuel condition of the engine, an engine method includes opening an intake throttle, modulating a reference voltage of an exhaust gas oxygen sensor, and experiencing a first change in sensor output during modulating. Then, during a second fuel-free condition of the engine, the method includes closing the intake throttle, modulating the reference voltage of the exhaust gas oxygen sensor, and experiencing a second change in sensor output during modulating. The method then generates an indication of the PCV flow based on the first change in the second change. Here, the first change in sensor output is a first change in the pumping current output by the sensor during open throttle modulation, while the second change in sensor output is a second change in the pumping current output by the sensor during closed loop intake valve modulation. The method further includes generating an indication of the ambient humidity based on the first change but not the second change in the sensor output.

Further, the first change may be a first average change, wherein generating an indication of the ambient humidity based on the first change during the first fuel-unconditioned condition, generating a change in pumping current for each modulation, averaging the pumping current, and generating an indication ambient humidity based on the average of the change in pumping current.

The method further includes, during a fueling condition of the engine after the first and second fuel-free conditions of the engine, adjusting an engine operating parameter based on both the ambient humidity indication and the PCV flow indication, wherein the engine operating parameter includes an amount of exhaust gas recirculation and / or an ignition and / or a fuel injection quantity and / or an air-fuel ratio of the engine. As such, during both the first and second fuel-free conditions of the engine, an opening, which couples a crankcase of the engine to the intake manifold, is closed. In addition, the wear of the piston valves is reported in response to the indication of the PCV flow being higher than a threshold.

In 7 the effect of PCV flow on moisture determination is shown. In particular, the graph shows 700 an exemplary change in the pumping current of an exhaust gas oxygen sensor at different reference voltages. The graphic representation 700 represents the DFSO conditions in the graph 702 , a reference voltage applied to the sensor in the graph 704 and a pump current output without PCV flow in the graph 706 with respect to the PCV flow output pumping current in the graph 708 represents.

From t0 to t5 a DFSO event of the engine can take place (the graphical presentation 702 ). In response to the DFSO event at t0, the reference voltage (Vref) applied to the exhaust gas oxygen sensor may be modulated between a higher voltage (such as 1080 mV) and a lower voltage (such as 450 mV), as in the graph 704 is shown. A pump current (Ip) output by the sensor in response to the application of the reference voltage can be observed. The graphic representation 706 (the darker line) shows the change in the pumping current of the exhaust gas oxygen sensor in response to the modulation of the reference voltage in the absence of any PCV flow such. B. when the modulation is performed with the intake throttle open. As in 710 is shown, in the absence of PCV flow, a smaller change in pumping current (delta-ip 710 ), where delta ip 710 corresponds to an inlet oxygen concentration due to the dissociated water molecules. Therefore, ambient humidity during the DFSO condition can be obtained from the Delta Ip 710 be derived.

The graphic representation 708 (the lighter line) shows the change in the pumping current of the exhaust gas oxygen sensor in response to the modulation of the reference voltage in the absence of the PCV flow, such. B. when the modulation is performed with the inlet throttle closed. As in 712 is shown, in the presence of the PCV flow, a larger change in the pumping current (Delta-Ip 712 ), where delta ip 712 an intake oxygen concentration due to both the dissociated water molecules and due to the dissociated CO ₂ molecules of the oxidation of the PCV hydrocarbons corresponds to the exhaust gas oxygen sensor. As can be seen, the presence of the PCV flow has a large effect on the output of the sensor, therefore one in the presence of PCV flow based on the Delta Ip 712 incorrectly estimate a higher ambient humidity than an actual ambient humidity. As in 4 explained, Delta-Ip 712 used to get the PCV flow rate. Specifically, by comparing delta ip 712 with delta ip 710 the impact of the PCV flow can be learned and the PCV flow can be deduced. Specifically, the PCV flow rate can be used as a function of the difference between Delta Ip 712 and delta ip 710 during the selected DFSO conditions.

At t5, the DFSO condition may end, fueling of the cylinders may be resumed, and the output of the sensor may not be used for moisture estimation. As such, during fueling conditions, the output of the exhaust gas oxygen sensor may be for estimating both an air-fuel ratio of the exhaust gases (as in FIG 3 discussed) as well as an ethanol content of the fuel combusted in the engine.

In one example, an engine system includes an engine having an intake and exhaust manifold, an exhaust gas oxygen sensor disposed in the exhaust manifold upstream of an exhaust catalyst, an intake throttle disposed in the exhaust manifold, a PCV port configured to supply the crankcase gases from a crankcase of the engine to the intake manifold; and a control system in communication with the sensor. The control system includes nonvolatile instructions to: close the PCV port during a fuel cutoff (DFSO) of the engine; to fully open the intake throttle; to modulate a reference voltage of the sensor between a first, lower voltage and a second, higher voltage; and generate an indication of ambient humidity based on a first change in pumping current in response to modulating the reference voltage. The controller further includes instructions to maintain the PCV opening closed; close the intake throttle completely; to re-modulate the reference voltage of the sensor; and generate an indication of the PCV flow into the intake manifold based on a second change in the pumping current in response to the modulating of the reference voltage with respect to the first change in the pumping current. Then, during a fueling condition of the engine after engine DFSO, the controller may adjust exhaust gas recirculation and / or engine air-fuel ratio and / or ignition based on ambient humidity.

In this way, an estimate of ambient humidity by an exhaust gas oxygen sensor during DFSO conditions can be accurately generated with a minimal effect on the moisture estimate from the PCV flow. Closing the throttle during DFSO conditions, as the humidity is estimated, reduces the PCV flow of the engine and reduces the effect of hydrocarbons of the PCV flow on the sensor output. During the same DFSO conditions, by modulating the sensor reference voltage with both the inlet throttle open and the inlet throttle closed, the change in pumping current at the sensor can be used to advantage in order to know the PCV flow to the engine. Not only does this enable the PCV flow to be measured, it also allows for early identification of engine component wear and engine aging resulting in PCV hydrocarbon leakage. One or more engine operating parameters may then be adjusted in response to the ambient humidity estimate and the PCV flow estimate. Since a DFSO may occur numerous times during a drive cycle, a measurement of ambient humidity may be generated multiple times throughout the drive cycle and one or more engine operating parameters adjusted accordingly, resulting in optimized overall engine performance regardless of fluctuations in ambient humidity. In addition, the operating parameters of the engine may be adjusted in response to the ambient humidity regardless of duration of the engine fueling conditions, since an indication of ambient humidity may be generated by modulating the reference voltage in a short period of time even if the exhaust is not free of residual combustion gases is.

Claims (20)

A method for an engine system, comprising: during non-fueling conditions of the engine when at least one intake valve and one exhaust valve are operating: Modulating a reference voltage of an exhaust gas sensor with an open and a closed intake throttle; and Indicating engine wear based on crankcase ventilation (PCV) flow, wherein the PCV flow is based on the outputs of the sensor during modulating. The method of claim 1, wherein opening the intake throttle includes full opening of the intake throttle. The method of claim 1, wherein the exhaust gas sensor is an exhaust gas oxygen sensor. The method of claim 1, wherein modulating the reference voltage comprises switching the reference voltage between a first, lower voltage and a second, higher voltage. The method of claim 1, wherein indicating engine wear based on the estimated PCV flow includes indicating engine wear based on the estimated PCV flow that is greater than a threshold. The method of claim 5, wherein modulating the reference voltage of the exhaust gas sensor with the intake throttle open and first open first modulating the reference voltage between the first and second open throttle voltage, then closing the inlet throttle and then modulating the reference voltage between the first and second intake valves second voltage with the inlet throttle closed. The method of claim 6, wherein estimating the PCV flow based on the outputs of the sensor during the modulating comprises estimating the PCV flow based on a difference between a first change in the pumping current output by the sensor during modulating with the intake throttle open , and a second change in the pumping current output by the sensor during modulating with the inlet throttle closed. The method of claim 7, further comprising generating an indication of ambient humidity based on an exhaust port open throttle output. The method of claim 8, further comprising adjusting an operating parameter of the engine based on the indication of the ambient humidity and the estimated PCV flow. The method of claim 9, wherein the operating parameter of the engine comprises an amount of exhaust gas recirculation, and wherein adjusting an amount of exhaust gas recirculation reduces the amount of exhaust gas recirculation in response to an indication of higher ambient humidity and / or an indication of a PCV flow greater than is a threshold. The method of claim 1, wherein the non-fueling conditions of the engine include fuel cutoff (DFSO). A method for an engine, comprising: during a first condition without fueling the engine, opening an intake throttle, modulating a reference voltage of an exhaust gas oxygen sensor, and experiencing a first change in sensor output during modulating; during a second condition without fueling the engine closing the engine Intake throttle, modulating the reference voltage of the exhaust gas oxygen sensor, and experiencing a second change in sensor output during modulating; and generating an indication of the PCV flow based on the first change with respect to the second change. The method of claim 12, wherein the first change in sensor output is a first change in the pumping current output by the sensor during open throttle modulation, and wherein the second sensor output change is a second change in the pumping current output by the sensor during closed loop throttle modulation , The method of claim 13, further comprising generating an indication of ambient humidity based on the first change but not the second change in the sensor output. The method of claim 14, wherein the first change is a first average change, and wherein generating an indication of the ambient humidity based on the first change during the first non-fuel condition comprises: Generating a change in pumping current for each modulation; Means for changing the pumping current; and Generate an indication of ambient humidity based on the average of the change in pumping current. 15. The method of claim 15, further comprising, during a fueling condition of the engine after the first and second fuel-free conditions of the engine, adjusting an operating parameter of the engine based on both the ambient humidity indication and the PCV flow indication the engine operating parameters include an amount of exhaust gas recirculation and / or an ignition and / or a fuel injection quantity and / or an air-fuel ratio of the engine. The method of claim 12, wherein both during the first and during the second condition without fueling the engine, an opening, which couples a crankcase of the engine to the intake manifold, is closed. The method of claim 17, further comprising indicating the wear of the piston valves in response to the indication of PCV flow being greater than a threshold. An engine system comprising: an engine having an intake and an exhaust manifold; an exhaust gas oxygen sensor disposed in the exhaust manifold upstream of an exhaust gas catalyst; an intake throttle valve disposed in the exhaust manifold; a PCV port configured to supply the crankcase gases from a crankcase of the engine to the intake manifold; and a control system in communication with the sensor, the control system comprising nonvolatile instructions to: during a fuel cut-off (DFSO) of the engine to close the PCV port; to fully open the intake throttle; to modulate a reference voltage of the sensor between a first, lower voltage and a second, higher voltage; and generate an indication of ambient humidity based on a first change in pumping current in response to modulating the reference voltage. The system of claim 19, wherein the controller further includes instructions to: keep the PCV opening closed; close the intake throttle completely; to re-modulate the reference voltage of the sensor; and generate an indication of the PCV flow into the intake manifold based on a second change in the pumping current in response to the modulating of the reference voltage with respect to the first change in the pumping current; during a fuel-priming condition after the engine DFSO Adjusting the exhaust gas recirculation and / or the engine air-fuel ratio and / or the ignition based on the ambient humidity.

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