What's wrong with Buick Excelle's unstable idle speed?

The reasons for the idle speed of Buick Excelle are as follows:

Throttle oil accumulation and throttle carbon accumulation, dirty air inlet:

Blocked air intake will cause unstable idle speed, and there is carbon deposit or engine oil in the throttle, which is the most common reason for unstable idle speed. The carbon deposit on the throttle will affect the opening and air intake, making the engine speed fluctuate after the cold start of the car, which is very unstable and accompanied by strong jitter. Serious oil or carbon accumulation in the throttle valve, including unclean air intake, makes it difficult to start the car in cold weather. The throttle is dirty and needs to be cleaned. Cleaning the throttle itself is also a daily maintenance item.

Failure of a single spark plug causes the spark plug to be unstable:

Spark plugs will also deposit carbon, which can be cleaned up and restore the activity of spark plugs. However, some spark plugs will lose their performance as they approach their service life. The weak spark of spark plugs in individual cylinders will affect the performance of automobiles. Spark plug failure will cause "fire" symptoms of the car, but slight spark plug failure of individual cylinders will cause idling instability symptoms. Therefore, cleaning or replacing the spark plug is also an option to solve the problem when the idle speed of the car is unstable.