Fast Idle (Diesels/Runs On)

WARNING: This page is about a different car, the 2000 Ford Pickup, 2000 Ford F550 Super Duty, 2000 Ford F450 Super Duty, 2000 Ford Contour, and 2000 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

Check mass airflow sensor for cracks, vacuum hoses, lines and throttle body for vacuum leaks. Check EGR valve and IAC valve for proper sealings.
Check air intake system, see TEST HU under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V (GASOLINE) article.
Check engine cooling system. See appropriate ELECTRIC COOLING FANS article in ENGINE COOLING.
Check A/C system. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
If engine idles fast at idle, turn ignition off. Turn ignition switch to ON position. Using scan tool, select TP V and TPREL PIDs from PID/DATA monitor menu. Check the following PID values: TP V and TPREL while wiggling TP sensor circuits. At vehicle start, TPREL PID reading will begin at about 1.25 volts and count down to the 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 volts greater than TPREL value at closed throttle, PCM will go into part throttle mode. Check for loose or worn throttle plates. If no concern is found, see TEST Z under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V article and check for intermittent faults.