Car idles at 3500 RPM!!! What is going on here?

[BlueOvalStangGT]

I drove to do some community service this morning and after I got on the interstate, the revs wouldnt go down. I had to turn it off at every light and no give it gas when driving( its like a permanent cruise control). What happened? Haynes says it could be a sticking cable( but it moves fine), a vacuam leak( still pulling plenty of inches of vacuam) or a fuel system or engine control system problem. What else? Eades suggested TPS mighta died on me. Im gonna go check that now. Any ideas? I need this car for prom next weekend!

 

[R.J.]

I've seen a bad Idle air control valve cause a SN95 to idle at 3000 rpm!

 

[BlueOvalStangGT]

Ok jsut played with it a little. That little stop on the left hand side( when looking down and from the front of the car) on the TB, is that a good way to adjust the idle? I thought that the EEC controled the idle and no matter what you set that stop at, the EEC would change it to its needs. I adjusted that stop and it idles at 700 now. I think maybe when i was cruising on I 95 maybe when the TB was open, the lil stop rattled its way down so when I closed it after I got off 95 it only closed so far. But then that wouldnt explain why it idled at 3000 for a little and then 2000 and finally at 3500. Whats a good idle speed for a supercharged car? It used to idle at approx 850 but the supercharger is really really loud at that RPM so a little lower would be nice but I dont want to hurt anything.

 

[WhiteDevil]

The car will bring iself back to 600rpm base idlein the computer. To a point if u opened it up enough it might not be able to correct that far. But it will try. I have a tweecer and i set my idle for 800rpm but when i set my new tbody like it says on EEC Analyzer it was at first idleing at like 900 after a couple drives it brougt itself back down to 800.

 

[mo_dingo]

That sounds exactly like what happened when my IAC valve was stuck open.

If you determine that it is bad, then you need to replace it with a ford piece or borg-warner one from pep boys. Mine from pep boys works great and has been for some time now.

Disconnect the connector from teh IAC valve and start the car. If it still idles high then the comp is not the likely problem.

If you remove the IAC valve and block off both ports with some tape, then start the car, the RPM's should not stay that high, or your car will not even start unless you hit the throttle while cranking. If that is the case, your IAC valve is probably bad.
Scott

 

[BlueOvalStangGT]

Figured it out. I guess when the car was cruising the and the TB open the little stop screw i guess wiggled loose and slides down slowly. Then when you let off the gas it cannot close completly and idles high. I got of I 95 again last night after I fixed it once and the revs jumped t o5k before I turn it off. First problem with the PRO Products TB. Fixed by sliding a nut on it and tightening it to the idle speed I want.