Check for engine vacuum leaks. The most common one is behind the throttle body. A 90 degree bend in the line dry rots and leaks. Not easy to find if you're not looking for it. If you find there are no leaks, check or replace the idle air control valve (IAC). The IAC is responsible for maintaining the engine's idle speed.
Tuesday, September 8th, 2015 AT 7:27 PM