Is my IAC bad?

Theres a specific idle reset procedure that can be found on many sites, probably even here. I had to do it when I first got my car. May want to look into that. Could also check for vacuum leaks.

Did you check the fuel system? Your problem sounds like mine. I found that my fuel pressure is maxed out all the time, regardless of vacuum, which means the FPR could be bad or the return line is clogged. I'll find out tonight if it's what is causing my surging and rough/lopey idle.

If you havent done the procedure outlined at this site ... Ford Mustang Base Idle Reset
I would do that before going much further.

I was experiencing very similar problems with my car. Back then it was still AODE. Half the time when I went from park to reverse it would stall. Under parking lot turning it would stall. Again, my first thought was IAC. But I happened to do the exact smae reset procedure as outlined in that site... and havent had a problem since. Just some food for thought.

If the car was not up to temp when you ran codes, you can get 116.

Hi, I'm a new member here, but this looks like the proper thread for this question. I have a 95 GT 5-speed that I've owned for almost 6 years now, and I've never had any major problems with it. The only things I have replaced on it are the fuel filter, SP wires, distributor cap, rotor, and ignition coil about a year and a half ago in a futile attempt to fix what turned out to be the PIP sensor. I used to have this occasional idling problem only in the winter where sometimes when I would put it in neutral, the rpm's would hover in the 2-2.5k region and would only come back down to almost normal when I would come to a stop. I say almost normal because I've forged a strong bond with my car and I know when it's not acting quite right, normal is pretty much dead on 1k and I can tell it's acting up if its up in the 1.1-1.2k area. I haven't had this problem for a while, and it started up a few weeks ago and got progressively worse(meaning it was happening virtually every time I took the car out), I should mention that the weather is far from cold, so this was even more unusual. After reading through many threads, I narrowed down the problem and I removed and sprayed the IAC unit and the intake ports. For good measure I also cleaned and recharged my K&N air filter and checked the MAF for build-up and removed my battery cables, cleaned the terminals and left it disconnected while doing everything else to (hopefully) reset the computer so I could attempt to have the car "relearn" its idle. I put everything back together, took it out for a test drive and it was still doing the same thing. I guess I should mention that within the past few weeks, the CE light has come on a couple of times, but has always gone off. I don't have a tester, so I haven't pulled any codes off of it but I was under the impression that those codes don't get stored on 95's and earlier and the best way to pull them is if the problem is happening at the time, but I could be wrong. Anyway, as I said I'd been reading all these threads and what I did was when I came back from the drive, I left the engine running, popped the hood and disconnected the IAC plug. I have read conflicting opinions on what should happen when you do this, but my car died almost immediately. I plugged it back in, started the car, and it has been absolutely fine after a couple of test drives. So my question is: what does that mean? Is that indicative of a failing IAC? I mean, I obviously had the unit unplugged while I was cleaning it, but that didn't seem to do anything, so why would it affect it just because I unplugged it while it was running? Also, what is the easiest way to remove this unit? Because it was a beyotch getting to that bottom bolt with the fuel lines in the way and I had to get it out at like 1/4 turn a time. Thanks in advance and sorry for the long post, just wanted to be as thorough as possible.

Dude....I just had a similar experience. The vacuum line from the purge valve, had come off the bottom of the intake....slid it back on, good to go...not sure if you checked that, but couldn't hurt..

You don't need a code reader to dump the codes, a paper clip will do. No matter what year the Mustang is, there is always some useful information in the code dump.


You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 200,000 hits, which indicates it does help fix idle problems quickly and inexpensively.