A mileage of about 70 thousand km, equipped with QR25 engine Dongfeng Nissan Chun Jun T30. Users reflect: the car appears idle shivering phenomenon. Fault diagnosis: to diagnose the car, there is a fault phenomenon as follows: no fault code, the rotation speed between 650 and 780r/min, the pulse width of 3.8ms (normal value 2.5ms), the air flow meter is larger than the normal value, the ignition time is unstable, the oxygen sensor and the water temperature signal are normal, using the computer to do the VAT test When the engine immediately flameout, feel the engine power is insufficient, but there is no obvious lack of cylinder feeling when accelerating. Next to the car carried out specific investigation, the intake system has no gas leakage, blocking phenomenon, cleaning the throttle valve, the exhaust gas is normal, the fuel injection head does not drop oil, the four fuel injection is basically the same, the replacement of four spark plugs, ignition coils and air flow meter, the failure is still. When comparing data with a similar car, it is found that the data of the malfunction vehicle is INT/V TIM100 CA, while the INT/V of the normal vehicle is 0~2 degree CA. After consulting the relevant information, we know that the number of teeth of crankshaft sprocket is 37, 9.73 degrees per tooth (360 37=9.73). The data INT/V TIM100 CA is very close to 9.73 degrees. The timing of the timing of the car should be checked. After opening the front cover of the engine, it is found that the crankshaft sprocket is just wrong. After replacing the relevant accessories of a set of timing chain mechanism, the trouble is eliminated.