The idle air control valve on your car or truck works by adjusting the airflow inside your vehicle's throttle body in order to control the engine idle. The idle air control valve commonly develops problems due to carbon build-up and blockage caused by exposure to the gases and debris from the engine's operations. You may notice several different problems with your vehicle in the event that your idle air control valve stops functioning properly.
One of the problems associated with a clogged idle air control valve is stalling. The stalling will occur because the correct amount of airflow is not getting through the intake due to the clogged valve. This will cause your vehicle's engine to stall out unexpectedly. This will typically occur while idling or at low speeds and should not be as much of an issue at high speeds.
A partially malfunctioning or clogged idle air control valve will cause your vehicle not to idle properly. The vehicle's idle is the main thing your IAC valve controls, so problems with the valve will affect the way the vehicle idles. In some cases the vehicle sounds like it is about to stall out and then idles at a higher than normal rpm, only to drop back down a moment later.
Runs After the Engine is Shut Off
If you turn your vehicle off and the engine continues to run for a moment or two, there is a good chance your vehicle has a faulty idle air control valve. The IAC is causing a lag between you turning off the key and the engine receiving the message to cut off and stop working.