What is the problem with abnormal noise when the engine is idling?

Cause of abnormal engine idling noise: 1, abnormal noise caused by excessive fit clearance.

Fit clearance is an important index of automobile assembly quality. Under the condition of constant lubrication, temperature, load and speed, with the increase of fit clearance, abnormal noise will become more obvious. Some parts of the engine will produce abnormal noise due to the increase of clearance caused by wear, such as knocking noise of piston and cylinder wall, impact noise of connecting rod bearing and journal, etc.

2. The engine cylinder makes abnormal sound.

Engine cylinder shortage mainly refers to the abnormal operation of one or more cylinders of the engine, which is generally manifested as: the exhaust gas flow discharged by the automobile is obviously intermittent, and the exhaust pipe is severely shaken, and the engine "chug" sound or plop, plop sound can be clearly heard. This phenomenon is closely related to the failure of ignition coil.

3. Abnormal knocking sound of engine cylinder

When the car starts to knock on the cylinder, the piston knocks on the cylinder, which means that the piston swings or jumps in the cylinder when it moves up and down, and its head or skirt collides with the cylinder wall and cylinder head to produce abnormal noise, which can be divided into cold knocking, hot knocking and cold knocking. At present, the cause of abnormal idling noise in housing has not been determined, which may be caused by the above reasons.