When I start my car, the RPMs go up and down, over and over. Also, when I turn off my car, it makes a noise.
This is most likely caused by a faulty Idle Air Control valve (IAC valve). This valve regulates the speed of the engine's idle by creating a controlled vacuum leak in the intake manifold. It is also possible that there may be a vacuum leak that is simulating a bad IAC valve. I would ask for help from one of the mechanics at YourMechanic to come to you and diagnose why your car does not maintain a consistent engine idle speed.
Have a car question? Get free advice from our top-rated mechanics.
Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%