Intermittent High Idle

[DanVB1]

My 97, 125K has an intermittent high idle, usually in the morning after I exit the highway going to work. I have shut off the engine in the parking lot, restart and things went back to normal.
This morning, happened again and disconnected IAC valve wire and idle returned to normal. Plug it back in, high idle.
I bought a new IAC today ($40), but still want to be certain that's the culprit. In another thread, soemone mentioned that this condition sounds like cold-high idle, maybe the temp switch being bad.
Otherwise the engine runs and idles well. Cleaned the IAC a few weeks back, but it didn't look dirty.

 

[twxsby]

mine did the same thing, but only when cold. I cleaned the IAC and that fixed it for several weeks, then back to high reving. I bought a new IAC, problem solved. (94 3.0)

 

[DanVB1]

I am going to install the new one this weekend, regardless. I will let y'all know.

 

[RumpRanger98]

I put a new IAC on my 99 3.0 because it seemed to have a high (1500) idle only after it was warmed up. Didn't help me, I still dont know whats causing it.

Make sure you check for vaccuum leaks and eliminate the easy stuff first.

 

[snoopdoggie]

I had a similar problem on a 2.3 and replacing the Throttle Position Sensor cured things.

 

[DanVB1]

Changed the IAC valve, runs as smooth as silk!
I took the small cap off the old unit and it looks like there is a felt air filter of sorts underneath.
I wonder if this is the cause of problems when it gets dirty?