Crazy Idle Need help please!

[dwsykes]

My brother has a 11/86 Ranger 5spd w/manual t-case that was pulled out of the woods in 1998 and the motor was rebuilt (the truck was overheated twice and the engine seized - guy pushed it into the woods). Ran fine till a few years ago. It sometimes does this crazy idle. The only way I can explain it is that it, as soon as you crank it, shoots up in RPM and then rapidly goes to the normal high idle RPM. Lets say (since no tach) it goes to 3,000 RPM and then down to normal high idle (RPM based on sound of my 88). Several sensors have been replaced at a Ford dealership over time. Nothing seems to work, and no one knows what to do. Oh and no flashing check engine light or trouble codes either. Usually after this it runs normal. Please! Anyone with any idea what is making this happen?

 

[Cyberbeer]

Try cleaning the Idle Air Control Valve.

 

[dwsykes]

This sensor...been replaced along with TP sensor
EDIT: A year ago or less

 

[Ranger4657]

anyone have any suggestions on cleaning the IAC valve? as it is expencive to buy a new one... myne is all gunked up with carbon build up and i dont know what to clean it with or a procedure?

 

[dwsykes]

I took one on my 88' and took the electronic part off (two screws, but be sure not to put it on backwards) and cleaned the mechanism with carb cleaner...it worked great.

 

[Ranger4657]

oh ok, ill give that a try here soon see how it does...

 

[dwsykes]

And the best of luck to you!

 

[Ranger4657]

dang that sucker was dirtyy!!!! shes runnin alright now though... hope it stays that way!!!

 

[Cyberbeer]

Might have a leaky injector..sadly I believe the only way to test the actual flow is to pull them out.

 

[BlackBII]

In order for it to rev to 3000 rpm, it has to be ingesting a hefty amount of air. Either through the IAC or the throttle body...

How does it act with the IAC unplugged?

 

[dwsykes]

I don't know but when I find out I will post the results. Here recently it is acting normal, past day or so. I am getting tired of this . Thanks guys been working late also.....

 

[dwsykes]

Called my brother and he is going to work with it tomorrow, so about 7:00pm I should have some info if not sooner.