How to Tell If the Idle Control Valve Is Bad?

1. Start your car, and listen to the idle. Does it sound faster or slower than usual? Does it 'stumble?' All of these things are symptoms of a failing control valve.
2. Locate the idle control valve on the intake. In every car they look different so refer to the repair manual of your specific car to know what it looks like.
3. Remove valve from the intake and clean with carburator cleaner. It will probably be covered with black varnish so some amount of cleaning will be necessary. Once clean, reinstall.
4. Start the car and determine if the engine's idling has improved. If the idling has not improved, you may need to replace the ICV.