All of a sudden car has high idle?

[DaveB]

Well I dont know what happened, but all of a sudden my car has an idle of about 1400 rpm. Just happened out of no where. I let me car sit idling outside CVS while I ran inside, it was at the regular ~800. I come outside and all of sudden its at 2000 once I push the clutch inamnit: . Can this really just happen out of no where like that? Once I get the car inching along and the rpms drop, as soon as I press the clutch back in, it jumps up to 2000, then back down to 1400. Anyone know what could cause this? Car has 110k miles and is stock except for bolts ons. Stock maf, tb, injectors, etc. I did a search but all of them dealt with people that either had blowers or had just done a mod that had caused the problem. Any help would be appreciated. Ahhh this and other crapola is really making me want to sell this thing .

 

[CManT1914]

Pull the codes. Then check your TPS (throttle position sensor, should read .98 volts with closed throttle) and IAC (idle air control) valve.

http://www.muscularmustangs.com/iac.php

That's a good writeup on resetting your idle. I bet the problem is in their somewhere.

 

[95cobradude]

check for vacuum leaks

 

[robtmc]

IAC is stuck, or has a crack internally. Had this exact thing happen on my 94 GT @ about 69k miles, no warning. It looked like the flexible metal bellows (accordian like thing) had cracked and was leaking a lot of air in at idle. I verified this by removing the IAC and blocking the TB air passage for the IAC. Idled riight down where it should. Pulled the IAC off my stock TB and it was fine again.

 

[BlackVert]

I bet it is that the IAC is stuck open too. They are like $40 bucks at autozone.

About selling it, IMO these are the coolest cars you can get for the money, especially the vert. I'll never sell mine, unless I win the lottery or something and I can buy a 03 Cobra or a 2005+ Cobra.

 

[HISSIN50]

I'll never sell mine, unless I win the lottery or something and I can buy a 03 Cobra or a 2005+ Cobra.

In which case, the snake would augment your existing ride, not replace it.

 

[mo_dingo]

Yeah, remove the IAC and tape off both passages. If the idle speed returns to normal, IAC valve is bad, and you need to replace it.

The one from autozone will not work. Go to pep boys, and get the one that looks like your factory one. It's a reman I believe, and it fits 100% without any mods.
Scott

 

[SeventyMach1]

Yeah, remove the IAC and tape off both passages. If the idle speed returns to normal, IAC valve is bad, and you need to replace it.

Or ..... you might be able to clean it & make it work. Unless the electrical side has a problem .... you should be able to fix it. They usually don't have a mechanical failure ..... they just get dirt/grime up in there that needs to be removed. Try to clean the valve side out with some t/b cleaner, Seafoam, etc. I had this same problem when I first got this '94 & the clean up did the trick. Hope you get it back to normal.

 

[WHITE94COBRA]

I just replace mine (a week ago) I bought a stocker from ford for 119.00 the pep boys all around me had none. fixed my idle right up...

 

[BlackVert]

Or ..... you might be able to clean it & make it work. Unless the electrical side has a problem .... you should be able to fix it. They usually don't have a mechanical failure ..... they just get dirt/grime up in there that needs to be removed. Try to clean the valve side out with some t/b cleaner, Seafoam, etc. I had this same problem when I first got this '94 & the clean up did the trick. Hope you get it back to normal.

they don't clean well ... at least mine didn't. mine was stuck open so i cleaned it. it was ok for maybe a week, and then it started sticking either open or closed, changing from one to the other at random times. it was really disconserting and scary.

 

[DavidNC]

Yeah, remove the IAC and tape off both passages. If the idle speed returns to normal, IAC valve is bad, and you need to replace it.

The one from autozone will not work. Go to pep boys, and get the one that looks like your factory one. It's a reman I believe, and it fits 100% without any mods.
Scott

The one I got from autozone last week works fine, and comes with 1 yr warranty. was $60.

 

[mo_dingo]

The one I got from autozone last week works fine, and comes with 1 yr warranty. was $60.

The one I got from autozone doesn't work. You have to mount it backwards, and my oil fill was hitting it, so it wouldn't bolt up. Let me know what you had to do to get it to work.
Scott

 

[DaveB]

Wow thanks for all the responses guys:SNSign: . I havent had time to look under the hood yet, should have time with the Thanksgiving break coming up. And for selling it, that was just me venting some frustration. And about selling it, that was just me venting some frustration. I have some big plans (and boost #s ) once I graduate in may and have a good paying job.

 

[fawcett]

what effect would an exhaust leak have on idle issues? i have a leak up front in one of my headers and my idle is at like 1400rpms. it sucks that the idle is so high but since my computer hates my e-cam its the only way to give my car some street manors.

either way, i am taking my car to the shop on monday to have the exhaust problem fixed. will this help my car idle better? i am already getting some really bad backfires when my engine winds down from like 4500rpms to 2500rpms. i think i may even be shooting flames!
i know ill find out on monday night, but i would like to know before hand if fixing my exhaust will help lower my cars idle.
-fawcett

 

[CManT1914]

fawcett, if the leak is bad enough, it can cause you to run rich enough to shoot flames out. When my EGR bung was uncapped, I would shoot flames out during WOT shifts.

 

[final5-0]

In which case, the snake would augment your existing ride, not replace it.

You said it JT

That would be the ONLY way I have one of those mod motors

NO WAY in hell I'd give up my push rod Stang for one of em

Then again there ain't no way any of that could happen cause I only got a two holer garage

Grady

 

[silv00]

Fixed it right up

Had the same thing - I found a good article on cleaning the IAC, so I thought I'd try that before buying a new one - worked like a champ.

http://www.muscularmustangs.com/iac.php

BTW - Pep Boys sells new ones for $49.95