Fast Idle (Diesels/Runs On)

WARNING: This page is about a different car, the 2002 Ford Pickup and 2002 Ford Cab & Chassis. 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 RUN circuit shorted to power and/or VPWR circuit shorted to power. See WIRING DIAGRAMS article.

Check base engine for air leaks, including proper sealing of intake manifold and components attached to intake air; such as EGR valve or IAC valve.
Check air intake system. See TEST HU: AIR INTAKE SYSTEM under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Check cooling system for overheating. If cooling system is overheating, repair as necessary. See appropriate ELECTRIC COOLING FANS article in ENGINE COOLING.
Check A/C system. See AUTOMATIC AC-HEATER SYSTEMS - BLACKWOOD & F150 or MANUAL A/C-HEATER SYSTEMS - F150 article in AIR CONDITIONING & HEATING.
For a fast idle concern, turn ignition off. Connect scan tool to Data Link Connector (DLC). Turn ignition on. Using scan tool, access PCM and select TP MODE PID from PID/DATA MONITOR & RECORD menu. Monitor TP MODE PID while wiggling TP sensor circuits. With throttle closed, TP MODE PID should read C/T (closed throttle). If TP MODE PID is not C/T with throttle closed, select and monitor TP V and TPREL PIDs for sudden changes while wiggling TP sensor circuits. At vehicle start, TPREL PID reading will begin at about 1.25 volts and count down to lowest TP V value since engine start-up. If TP V value goes below normal range, then increases again, TPREL will set to lower voltage. If TP V is about .04 volt more than TPREL value at closed throttle, PCM will go into part throttle mode. Also check for loose or worn throttle plates. If no problem is found, check for intermittent faults. Go to TEST Z: INTERMITTENT under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.