Research On Misfire Diagnostic System Of Electronic Controlled Gasoline Engine

Engine emission regulations and fuel consumption regulations are increasingly stringent with the deterioration of global climate and the increasingly outstanding of energy problem, which bring new challenges to the emission control of engine. The study of on-board diagnostic (OBD) system has significance to cope with the new challenges to the emission control of engine.Supported by Technology Innovation Fund for the National Enterprises (Development and Commercialization of Universal Electronic Control Unit (UECU) for Engines, NO.08C26224302178), study on OBD system was carried out. The fault detection principle of the basic sensors such as throttle position sensor, intake air temperature and pressure sensor, coolant temperature sensor were introduced as well as the principle of the engine misfire detection, whose detection strategy and algorithm were fully analyzed, and the means of evaluating crankshaft speed was adopted.The diagnostic experimental platform was established base on the Universal Electronic Control Unit (UECU) along with the calibration software, all of which were designed by our topic-based group. In order to control the experimental gasoline engine with the UECU, parameter calibration was carried out on the platform.Misfire diagnostic function was embed into the software of UECU as well as the misfire control logic for the engine for the sake of the misfire diagnostic experiment. Diagnostic test on part of the sensors and actuators were carried out to validate the diagnostic algorithm. In order to validate the misfire diagnosis strategy, a fault reference was output to the fault annunciator station while misfire setting was carried out with calibration software. By compare the diagnostic result from the diagnostic strategy with that on the fault annunciator station, whether the diagnostic result is right or wrong can be demonstrated, and the result shows that the correct rate of misfire identification is higher than 90%.The emission performance test of the gasoline engine was carried out with different misfire rate and the mechanism was analyzed. When misfire rate rising from 0 to 3.5%, the content of CO and HC emission rising from 0.55%,332ppm to 4.37%,1327ppm respectively.