A Beijing modern Hyland car with a 1.6L G4ED engine in 2011. Owners reflect: the cold car is easy to stall when it starts. After receiving the vehicle, start the engine and find that the idle speed is normal, and there is no obvious abnormality. To find out the cause of the trouble, we first checked the throttle and found that it was dirty inside the throttle. Before washing, look at the data flow controlled by idle actuators. The data is 34.2%, and the data is 25.76% after cleaning. In the past, we used to clean the throttle according to the mileage. In actual work, we often encountered such problems. In communication with the owners, we found that the owner often reflected the maintenance items similar to the throttle cleaning. Sometimes the owner is wrong, sometimes it is just done, but if it is not really clean, there are other factors that cause the throttle and dirty, it is difficult to find the qualitative data basis. The throttle of this car is especially dirty before cleaning. The problem that the owner reflects should be the low idle speed in the cold car, or the narrow range adjusted by the idle speed valve, so it is easy to start out the fire phenomenon. By comparing the data before and after cleaning, it is possible to confirm that the throttle and idle motor of the car are really dirty, obviously affecting the intake volume, and can confirm this from the test data. The vehicle runs well in all aspects, and other data can also be used as a reference for future maintenance, such as the voltage of the throttle position sensor, the pulse width of the fuel injection, the running state of the fan and so on. In addition, special attention should be paid to the following four points when cleaning throttle. 1. when cleaning the Korean car, the throttle shaft and the back of the throttle valve piece are close to the throttle shaft, and there are some special glue to prevent the air leakage. This is the original car when it comes out of the factory. Do not remove it, otherwise the idle speed may be unstable. 2. throttle cleaning agent contains stupid, easy to cause irritation to the skin, so try not to contact the skin cleanser directly. 3. before and after cleaning, attention should be paid to testing data. If abnormal, further inspection and diagnosis should be carried out. 4. for certain models such as Volkswagen, American Buick and French car, it is necessary to carry out computer matching after the first throttle. Fault review: this case is relatively simple. As long as the engine control module data flow is read at idle speed, the fault code location can be found immediately. Because the idle control valve is dirty, the engine control module will control the idle speed control valve opening. According to the data flow provided by the author, the three way catalytic converter of the vehicle should be blocked because the signal voltage of the post oxygen sensor is 0.73V. The camshaft adapts 1 (124), the camshaft adapts 2 (302). The camshaft adapts 3 (480), and the camshaft adapts 4 (661.97) can see that the camshaft adaption value also appears a little deviation. The author can carefully analyze the data flow when eliminating this case, and the practice is correct, especially at the end. When the Korean car is cleaned, the throttle shaft and the back of the throttle valve piece are close to the throttle shaft, and there are some special glue to prevent the air leakage. This is the original car when it comes out of the factory and does not remove it, otherwise it may appear. The instability of idle speed is worth our attention.