A Japanese Nissan. After the car cleaned the throttle in other repair plants, the engine's idling speed was too high, and its rotational speed varied from 1500 to 2500r/min. Use the decoder to enter the system, read the fault code, display the "system normal", and then press the decoder's tips for idle learning, but the engine speed is still the above speed. After telephone consultation to the Jin Pentium maintenance station, it is suggested that the coolant temperature should be reduced to 70 C, then "work support", and then "idle air learning" is selected, and the following operation is carried out according to the above hints: the car comes with a high temperature and can see the temperature of 102 C at that time from the data flow, in order to get the engine as soon as possible. The temperature drop down, thinking is to use the water pipe directly to the engine temperature sensor, through the actual operation found that the temperature can be smooth down, but as long as a car, the engine cooling liquid temperature immediately rise to 80 degrees, so that can not guarantee the temperature of 70 degrees. It is considered that the heating function of the circulating cooling liquid in the engine is far more than the cooling effect of the external water pipe, because the external flushing is only partially cooled by the cooling liquid temperature sensor. As long as the surrounding hot coolant is circulating, the sensor will be heated again. Therefore, only after patiently waiting for the whole engine temperature to drop, can idling learning be carried out. When the coolant temperature drops to about 65 degrees, the idle speed is learned and the result is successful once again. Is coolant temperature 70 centigrade a critical condition? It needs later maintenance to verify.