My car has this strange behaviour.
When it's cold idle won't stay at one steady rpm. It goes to 1500 then back down (sometimes too low and it stalls) and then back up again and back down and up and down and so on. During this the SES light comes and stays on.
But when the engine is warm and I shut her off, then start her again idle is steady and no SES light.
What should I start looking for!!??
MAF or IAC or some relay or could it be something else considering that my car hasn't been used the last four years.
It's gonna get new plugs, oil, oilfilter, fuelfilter, soon but I think that won't solve this problem.

Any ideas? Thanks!!!!:hail:

 

I'd suggest you start by cleaning the throttle body and removing the IAC for disassembly and cleaning. Only a little varnish or dirt accumulation will stop an IAC stepper motor from moving. The photos shows the difference between a "dead" IAC that wouldn't react to inputs, and that same one that was fully functional after cleaning:

 

Thanks for the advice Vader!
But I do think that I found my problem in another place........my car seems to have a PROM from a '87 5.0 5 speed while it is a '89 5.0 5 speed. Between the two the '87 has a ninth injector for coldstarts and the '89 gives extra fuel on coldstarts via the PROM program. Now mine is not getting the fuel from the ninth injector (it has none) or from the PROM (cause the '87 PROM don't give extra coldstart fuel). So first I wanna get a correct '89 5.0 TPI 5 speed PROM and see what it'll do..............................

 

what do you use to clean those?

 

I use a mild spray carburetor cleaner (so it doesn't dissolve the insulation on the stepper motor windings) and a small, stiff brush.

 

where's the IAC located?

 

it's located on the side of the throttle body on an angle on 5.0's and behind the throttle body on v6's. 4 wire harness setup in square formation.

like this
___
|OO|
|OO|

 

vader come fix my car man. it's broke. How did you get that all apart like that? I'm about to throw mine on the ground.

 

Remove the IAC from the TB.

Carefully rock the pintle back and forth as you gently pull outward. Pulling too hard will only lock the gear teeth on the pintle into the gears of the stepper motor, and you'll be there forever removing it. It may take 2-3 minutes, but the pintle should eventually work all the way out of the stepper motor, as shown in the photo.

Once everything is clean and dry, apply ONE drop of clean engine oil to the pintle gear shaft, then reassemble the spring and pintle, and rock the pintle back and forth while gently pushing against the spring to work it back inward. Retract the pintle fully, so that the spring is fully compressed, before installing it back into the throttle body.

NOTE: On V-6 engines, there may be a specification for pintle length before installing the IAC, since the ECM won't just "learn" the pintle position on its own, like it will on the V-8s. I'm not sure what years of the V-6 engines require the length setting, but I've seen it in some manuals.