Idle Problems! PLZ HELP!

the1nonlyb

Registered User
Alright. When we start up our 90' Tbird SC, its quickly rises to about 3000 rpm in park. In 1 D or OD it will fall back down to the 500 rpm range. Yet whenever it is shifted into neutral or park it rises right back up to 3 grand. It started happening out of nowhere in the crappy tire parking lot today...

any suggestions? could it be the transmission? Maybe a vaccum hose is disconnected? Im lost.
 
the1nonlyb said:
Alright. When we start up our 90' Tbird SC, its quickly rises to about 3000 rpm in park. In 1 D or OD it will fall back down to the 500 rpm range. Yet whenever it is shifted into neutral or park it rises right back up to 3 grand. It started happening out of nowhere in the crappy tire parking lot today...

any suggestions? could it be the transmission? Maybe a vaccum hose is disconnected? Im lost.


I had a 1989 with a manual transmission. I had the same problem, changed the IAC, and TPS with no avail. Got to lookin and all it was was a pinched hose directly under the throttle body :D Hope this helps.
 
Disconnect the IAC.. if no change in idle speed, swap it out. Oh, Ford part or equivalent only.. most aftermarket IACs will not work on the supercoupe engine. That includes those sold by Azone, pep boys, Orielly, and Napa :eek: .. yes, even Napa has the wrong part. Ford and Advance sell the right part. There is a simple way to tell; if it doesn't look just like the part you have, it is wrong. :cool:
 
I disconnected the IAC, it dropped about 500 rpms, then reconnected it back up to 3 grand. then tapped it it droped to 2grand, disconnect it again and it stays at 2 grand. put it back on its back up the 3000.

I can't see any twisted or plugged hoses but Ill have a better look in the morning.

We may just go to our parts car and get the IAC from it, along with the other supercharger because we think ours has had it.

-B.
 
sounds like the iac to me just replaced mine yesterday for the same problem, got mine from advance works great.
 
well. we just got two sending units of 3.8 FIs and the IAC valve from our SC parts car...

putting it in right now. Ford wants $163 for a new IAC valve, but i think there bull****ting me.
 
the1nonlyb said:
well. we just got two sending units of 3.8 FIs and the IAC valve from our SC parts car...

putting it in right now. Ford wants $163 for a new IAC valve, but i think there bull****ting me.
Mine was about $70 couple of years ago from Ford. Try a reseller here. In the IACs that you ar trying out, be sure it has what looks like a white bellows (or spring looking thing) inside but don't touch it. Very brittle and will rupture and send your idle racing. If you must clean it, spray some carb cleaner inside and shake it around, but don't touch with anything including any sort of brush.
 
well, we got it fixed. it was the IAC Valve. We thought it was the sending unit, but I guess not..

Thanks for All your help everyone!
 
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