What is the reason for the car's ups and downs when idling?

What are the possible reasons for the high and low idle speed? The maintenance master of 4s shop introduced it to us.

First, the stolen goods produced in the air and the sludge produced by gasoline are likely to cause the vehicle throttle to be too dirty and the idle motor to work poorly.

Second, excessive carbon deposition can easily lead to lax valve closure, poor atomization of fuel injectors and insufficient combustion.

Third, the exhaust pipe is blocked, resulting in poor exhaust.

Reason 4: Air leakage leads to insufficient vacuum.

The fifth reason is that the circuit is aging and the computer board is broken, which is not easy to appear in the short term. Car owners are advised not to easily install other equipment for their cars.

Reason 6: Insufficient cylinder pressure and natural wear will not appear in a short time.