What is the reason for the unstable engine speed?

1, throttle oil accumulation and throttle carbon accumulation, air intake is too dirty.

Blocked air intake will cause idling, and there is carbon deposit or engine oil in the throttle, which is the most common cause of unstable idling. Due to carbon deposition, the throttle will affect the opening and air intake, which will make the engine speed fluctuate after the car is started, which is very unstable and accompanied by strong jitter.

The throttle valve has serious oil storage or carbon deposition, including unclean air intake, which makes it difficult to start the car in cold weather. When the throttle is dirty, it needs to be cleaned, and the throttle cleaning itself is also a routine maintenance item.

2, individual spark plug failure caused the spark plug spark is too weak.

Spark plugs will also deposit carbon, which can be cleaned to restore the activity of spark plugs, but some spark plugs will have poor performance when their service life is approaching.

The spark plugs on individual cylinders are weak, which will affect the performance of the car. We know that the spark plug failure will lead to the "fire" symptom of the car, but the spark plug failure of individual cylinders will lead to the idling instability symptom. Therefore, when the idle speed of the car is unstable, cleaning or replacing the spark plug is also an option to solve the fault.

Oil blockage and intake pipe failure represented by oil nozzle.

When the fuel passage represented by the fuel nozzle is blocked, it will cause insufficient fuel supply pressure, poor fuel atomization, unbalanced mixing ratio and incomplete combustion, which will lead to related failures.

If the intake pipe leaks air, it will affect the real data reflected by the air flow meter, resulting in inaccurate control of intake air volume by ECU, unbalanced mixing ratio and unstable engine idle speed. Oil cleaning is also a maintenance project, which we call engine health care. There is something wrong with the oil circuit, and the emission exceeds the standard, so the car can't pass the annual inspection.