Engine control and diagnosis system for motor vehicle internal combustion engine with exhaust gas recirculation

摘要

The system has a number of sensors (18) for measuring engine operating parameters and an exhaust gas recirculation (EGR) valve (16) for permitting exhaust gas to flow from the exhaust system (14) to the engine (10) air inlet system (12). A controller (20) opens the EGR valve during a number of successive test periods during which it measures the engine speed response through the sensors. The test periods are separated by nonuniform intervals and the controller increases or decreases the intensity of the test periods in the event that the measured engine speed falls below or is greater than predetermined threshold levels. The controller measures the engine speed response to the opening of the EGR valve by observing the engine's speed change during a number of predetermined windows that correspond to the timing of the test periods and by comparing the observed engine speed change to a rolling average of the standard deviation of the engine speed. An Independent claim is included for a method for determining proper operation of an EGR system of an automotive engine that has an EGR valve operated by an engine controller.