TOYOTA 4 cylinder and automatic transmission Jiamei sedan. The car is inexplicably flameout, and it is not easy to start after it is extinguished. In several 4S shops and several repair factories, there is no trouble shooting. Maintenance personnel generally adopt the method of cleaning nozzle, replacing spark plug, high voltage line, measuring cylinder pressure, cleaning throttle body, idle motor and so on. The owner describes that there are several flameout attempts to drive a car several times a day, and now more and more frequently. Fault diagnosis: with the owner of the trial run, I asked whether to block fire or neutral fire? Speed up or slow down? Switch off or step on the brake pedal? He said he didn't care. Through the trial run, the author found that when the neutral gear was stalled, the engine idling control problem was basically determined. The author also made a test to pull out the throttle position sensor to test the vehicle (the state of the throttle position sensor was first collected). The result of the experiment is that no flameout is found, and the owner does not know when the valve is mounted. At the time of trial run, the owner said that he would not feel out of action again. (he was an old driver with great experience in driving. Therefore, the idling control system can be identified as a failure. The characteristics of the engine structure are analyzed. The air supply system of Toyoda Kami car is used to measure the intake volume of the vacuum pressure type. The idle speed control is a by-pass control mode, and the idle speed motor is used to control the opening of the side channel. Remove throttle body for cleaning throttle and idle motor and adjust. First, adjust the idle speed signal to the throttle position one by one, adjust the leakage rate when the throttle is closed. After the assembly, the learning of idling initialization is carried out. Then test the car, the idle speed is normal, troubleshooting.