Hi Bert,
The idling system is not working correctly and possible causes are :
1. Idling speed adjusted too high. Turn idle adjust screw in fully and back out 1/2 to 3/4 turn and recheck idling speed
2. Vacumn leakages after the throttle plate. Check for disconnected hoses or faulty PCV.
3. Faulty Fast Idle Thermal Valve( FITV). Remove the air cleaner hose and just inside the throttle body you would find 2 ports. Start engine and warm up to operating temperature. Close the lower port with your finger or a piece of cardboard if it is too hot. If the idle stabilises and engine stops hunting, the FITV is not closing fully. It could be due to lack of coolant, clogged coolant hoses or the FITV internal valve has worked itself loose.
4. Faulty Idle control Valve. Close the upper port and if engine stabilises, the IAC is faulty or coolant hoses are clogged.
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Monday, August 9th, 2010 AT 1:07 PM