High idle, need help with idle control valve (IAC)

[idude2000]

Just joined the forum, but have been reading for a while. Hello to everyone.

I have a 2002 Expedition XLT, 4.6L, 2WD, 140k miles.

Idle has been high for a couple of weeks. When stopped and holding the brake in drive, around 1200RPM. Sitting in park, over 2000RPM. If I sit for over a minute it slowly starts to come down. Engine hot or cold it acts the same.

I have not been able to find a vacuum leak, but I am no expert. Just feeling around and wiggling lines. I don’t think it is a vacuum leak because why would it come down eventually?

So I want to test the idle control valve.
- What should the voltage be going to it? Is it variable? What voltage range? I have a variable power supply and want to see it accuate.
- What ohm reading should I get on the valve? Can someone check theirs? It is very easy to access.

Thanks for your help.

 

[ELVATO]

Try taking it off and cleaning it. Then, disconnect the battery for a couple mins, reconnect, and let idle for a couple minutes. Then, drive around. This is to reset the driving/idle strategy.

Did it just randomly start idling high, or was it a gradual thing?

 

[idude2000]

Just tried what you described, acted just the same. The problem started all at once while driving. Noticed the RPM was up without my foot on the accelerator. It has done it full time ever since.

 

[ELVATO]

Another thought, since the engine is cable driven. Does the throttle return immidiately when you let go of the gas? It might be sticking?

Take off the air intake at the throttle body. Move the throttle cable, and see if butterfly immidiately closes all the way. It might be gunked up? Spray some throttle body cleaner in there and clean with a rag. Ideally, you could take off the throttle body and give it a good cleaning. At your mileage, it's probably gunked up anyways.

 

[ssbroly]

My accelerator was sticken for a while, put a few paper towels under the throttle cable and blast a little WD in it. I did that about 2 years ago and never had a problem again.