Fast Idle, Diesels/Runs On

WARNING: This page is about a different car, the 2002 Mercury Villager. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: If vehicle runs normally after ignition is off, check for damaged ignition switch, IGN START/RUN circuit short to voltage, VPWR circuit short to voltage, and engine mechanical condition. See WIRING DIAGRAMS article.

Check for engine air leaks, including proper sealing of intake manifold and components attached to intake air, such as IAC valve.
Check intake air system. See TEST HU: AIR INTAKE & THROTTLE BODY under SYSTEM TESTS in SELF-DIAGNOSTICS - VILLAGER article.
Check idle air control system. See TEST KE: IDLE AIR CONTROL SYSTEM under SYSTEM TESTS in SELF-DIAGNOSTICS - VILLAGER article.
Check cooling system operation.
Check A/C system operation.
Check for intermittent faults. See INTERMITTENT PROBLEM DIAGNOSIS .