What Causes High Idle Problems?

The number one cause for high idle is an imbalance in air pressure. An engine that is idling too high may be caused by a faulty idle air control motor valve that has completely failed or that has simply become weak and is not functioning correctly.

Another cause of high idle could be the air intake boot which delivers air into the intake system. If it's broken or leaking, it can cause an imbalance and create high idle. The throttle must also be functioning correctly and be free of build-up. Inspecting the intake gaskets and engine vacuum hoses can often lead to the problem. If something is wrong with those, the appropriate course of action is to clean the lines or replace them.