After taking the car, the idle speed of the engine was measured to be 1400 r/min. In general, the reason that the engine idle speed is too high may be: the throttle is not strictly closed; the throttle position sensor has malfunction or improper adjustment; the idle air control valve has trouble; the coolant temperature sensor has trouble; the PCV valve has trouble; the intake system vacuum pipeline leakage gas and so on. First, the fault code is read by the fault detector and the trouble free code is displayed. The throttle position information, the air conditioning load information and the coolant temperature information are read out by the fault detector, and the data are also displayed normal. Then check and clean throttle body and idle air control valve stepper motor, engine idle speed remains the same. Then the vacuum meter is used to measure the vacuum of the intake manifold at 33 kPa (normal 64 kPa-67 kPa}, and the vacuum meter pointer has a small swing, which coincides with the air leakage fault characteristics of the intake system, and then focuses on the leakage point of the intake system. " First pull off the PCV valve and all the vacuum tubes on the intake camps, use tape to plug the vacuum tube interface on the intake manifold, and make the idle air control valve close the idle bypass air channel reliably, starting the engine (to the idle air control valve step motor unelectricity), the engine idle speed has no change, thus it can be judged not. It is a problem of vacuum pipeline. It should be the leakage of engine intake pipe system. And then check the intake manifold and its gasket. No abnormalities were found. Under the condition of engine idle speed, the oil drops in the third cylinder intake manifold liner are quickly disappearing and accompanied by the symptoms of "tonic" sound leakage when the oil pot is used to drop the oil in the gasket of the intake manifold of each cylinder. After the intake manifold was removed, it was observed that the intake gasket had ruptured. After changing the new gasket of the intake manifold, the idle speed of the engine is stable at 850 r/min, and the vacuum degree of the intake manifold is 66 kPa, which is troubleshooting.