RPM fluctuations
 

I have a question, last week when I went to leave for work after starting my 97 F150 4.6 auto 4x4 with 209k miles. I noticed the tach fluctuating up and down about 300rpms. It only does this on a cold start after sitting overnight. After it gets warmed up it doesn't due it. I was looking on the ranger forum, because another user is having similar symptoms. They guys there are thinking the IAC is the culprit.

One more thing also is that only on a cold start the rpms go to about 1500 and then fall back down. This is after the truck is running for a few seconds that it does it. I start it up and it settles to 1000 but then all of a sudden it jumps to 1500 and then falls back down to around 1000rpms.

Sounds to me like anothoer IAC problem. They are very easy to clean....some catsrol degreaser in the ports and let it sit for a few minutes. The only part I don't like is taking the throttlebody elbow off to get at it, the gasket is reusable but I bought another one from Ford and replaced it anyways, very inexpensive fix and worth a try.

Ok thanks xtr. I'll get around to it when it warms up a little. Lows around here in MN are expected to get into the mid 20s next week. It's only October!

anyone have a picture guide on cleaning the IAC?....but truck seems to do the same thing...but on the speedo...(i dont have a tach)

THNX
Duggy