high idle

[ThainC]

Merry Christmas All!

My mother has a 91 that she has been having problems with. Thanks to this site I rebuilt her shift.motor. i also cleaned the maf. And the iac. Sensors. The truck idles nice and smooth, but it seems high at 2k idle. Climbing to the 4.5k range quickly. Any thoughts? Sorry for the horrible construction of this post... on a phone r!

 

[Blacksheep Josh]

Try setting the TPS sensor possibly? It might be out of ranger causing a high idle.

 

[ThainC]

Hrm... will have to look that up. Not a Ford expert ;o) just been searching this forum!

 

[92exp4x4]

Wow, 4500 rpm for an idle, thats really high! You may have wedged something in or screwed up the IAC valve when you had it apart. Thats way not normal and dangerous. Normal idle is computer controlled and set about 700-900 RPM

Make sure The IAC valve moves alright and is not binding, did you replace the gasket? Although, the leaking air should not make the engine rev that fast. Are the throttle cables routed correctly, binding?

Check for codes, there may have been something else go bad. Did you unplug the battery and allow the adaptive learn to be "forgotten". Let it sit for about 10 minutes then hook it back up. The truck will relearn itself within about 25 miles of driving with the clean sensors and hopefully run much better.

 

[ThainC]

Back on a computer, so my texts will make sense. It seems to be sitting between 1.5k - 2k for the idle at all times now. I will take a look at the IAC - not sure how I could have messed it up since I couldn't take it apart - I just cleaned all the grime off of it with an electric parts cleaner. Same with the MAF.

I will take a look in a bit - but no, the battery was NOT disconnected now that I think about it.

 

[LXNavajo_94]

Are you saying you cleaned the MAF with an electric parts cleaner? There's really not a big deal cleaning it that way but you should really use a MAF cleaner. CRC brand is a good one I get it from the local Advance store. Some electric parts cleaners leave a bit of residue when they dry which could be causing your problem the first time I cleaned mine I had a bit of a high idle but I used electra clean that I picked up from work heck it was free lol. I then went to the store and bought the CRC brand maf cleaner fixed my high idle. Hope this helps

 

[MrShorty]

I haven't seen it mentioned yet, but one of the first things I would look for is a vacuum leak. Make sure all the hoses and caps are on the "octopus" at the back of the intake and that none of the hoses are leaking.

 

[Turdle]

Is there a chance the IAC valve was installed "upside down"? Seems likely, as this is the symptom of doing so.

 

[ThainC]

I'll pick up some MAF cleaner. I didn't think electric parts cleaner left residue - definitely just learned something.

I'll also check the vacuum hoses at the back.

As for installing the IAC upside down... Uhh... I don't think so. I mean... ... ... Odd. I am 99.9% sure I wouldn't do that, but you MENTIONING it suddenly has me doubting it as I can't VISUALLY see it in my head at the moment. Awkward. I'd say it's good... but none the less I'm going to look at it!

Thanks for all the insight.

Now if I can figure out why her temp seems to be going up and down quite a bit... that'll make me happy.