Methods and systems for diagnosing engine internal exhaust gas recirculation
Systems and methods for diagnosing operation of an internal exhaust gas recirculation system of an internal combustion engine are presented. The system and method may be applied to conventional or hybrid powertrains having a capability to rotate an engine via an electric machine. The internal exhaust gas recirculation system may be diagnosed based on output of a differential pressure sensor.
1. A method, comprising:
rotating an engine that is not combusting an air-fuel mixture and generating a difference between a sensor output with an internal exhaust gas recirculation (IEGR) system commanded to a baseline position and the sensor output with the IEGR system commanded to a non-baseline position in response to a request to diagnose the IEGR system, the sensor not used to operate the IEGR system; and
adjusting output of the engine when the engine is combusting air and fuel responsive to the difference.
2. The method of claim 1 , where the engine is rotated via an electric machine that propels a vehicle.
3. The method of claim 1 , further comprising rotating the engine in further response to a predetermined amount of time since occupants have most recently exited a vehicle.
4. The method of claim 1 , further comprising rotating the engine in further response to a vehicle that includes the engine being a human driverless vehicle.
5. The method of claim 1 , further comprising rotating the engine in further response to a request to remotely start a vehicle that includes the engine.
6. The method of claim 1 , further comprising rotating the engine in further response to a battery state of charge being greater than a threshold.
7. The method of claim 1 , further comprising rotating the engine in further response to a temperature of a catalyst being greater than a threshold.
8. The method of claim 1 , where a sensor is a differential pressure sensor configured to sense pressure across a particulate filter.
9. The method of claim 1 , where the IEGR system includes an intake cam and an exhaust cam.
10. A method, comprising:
rotating an engine of a vehicle that is not combusting an air-fuel mixture and recording a differential pressure sensor output value while an internal exhaust gas recirculation (IEGR) system is commanded to provide a baseline EGR amount in response to a request to diagnose the IEGR system and the vehicle being coupled to a stationary electrical power grid;
rotating the engine that is not combusting the air-fuel mixture and recording the differential pressure sensor output value while the IEGR system is commanded to generate a non-baseline EGR amount in response to the request to diagnose the IEGR system and the vehicle being coupled to the stationary electrical power grid; and
adjusting engine spark timing responsive to a difference between the baseline EGR amount and the non-baseline EGR amount.
11. The method of claim 10 , where the engine is rotated at a constant speed.
12. The method of claim 10 , further comprising regenerating a particulate filter in response to the request to diagnose the IEGR system.
13. The method of claim 12 , where the particulate filter is regenerated when the engine is combusting air and fuel at a time before the engine is rotated while not combusting the air-fuel mixture and recording the differential pressure sensor output value.
14. The method of claim 13 , where the particulate filter is regenerated via increasing exhaust temperature via retarding spark timing.
15. A vehicle system, comprising:
an engine;
an electric machine in mechanical communication with the engine; and
a controller including non-transitory instructions executable to rotate the engine via the electric machine without supplying fuel to the engine in response to a request to diagnose an internal exhaust gas recirculation system, and indicating degradation of the internal exhaust gas recirculation system based on sensed operating parameters from sensors independent of those sensors used to operate the internal exhaust gas recirculation system.
16. The vehicle system of claim 15 , where the internal exhaust gas recirculation system includes an intake cam and an exhaust cam.
17. The vehicle system of claim 15 , further comprising additional instructions to combust air and fuel in the engine and regenerate a particulate filter in response to the request to diagnose the internal exhaust gas recirculation system.
18. The vehicle system of claim 15 , further comprising additional instructions to rotate the engine via the electric machine without supplying fuel to the engine in further response to a vehicle being coupled to a stationary electrical grid.
19. The vehicle system of claim 15 , further comprising additional instructions to rotate the engine via the electric machine without supplying fuel to the engine in further response to a temperature of a catalyst being greater than a threshold temperature.
20. The vehicle system of claim 15 , further comprising additional instructions to rotate the engine in response to a driver removing a vehicle key or leaving a predetermined proximity of a vehicle in which the engine operates.