[Gallie]

1991 5.0 all stock with 180,000 miles. I replaced the IAC and disconnected the battery to ensure a computer reset. It did not fix the problem, which is as follows:

- Cold starts are fine and holds a higher idle until warmer.
- When warm the idle lowers to around 800 rpm or so (normal) and idles very smooth. This will continue for some time 20 plus minutes or so.
- I'll be sitting at a light and suddenly something turns on, or off or some setting is implemented and the idle suddenly drops...the car runs very rough with a mis.
- It remains like this from this point on, until my next cold start up, etc.

I'm tired of driving with 2 feet to prevent stalling!!!

The IAC is the only part I've replaced and the Engine Light has been flashing for the past years, even when the car didn't do this.

Anyone else have the same problem and a solution? I will try the EGR valve next and then go from there, but any help would save me time and money.

Thanks,

Gallie

[TurboLX]

yea i was just gonna say EGR but thats hould really have no affect, maybe the wiring for the IAC is no good

[SALIV8]

Chceck your codes, you really should fix whatever is settin the check engine light.

[cobraetti]

Mine did(i hope) do this in the past. I would definatly check for codes. I cleaned the ECT sensor and replaced the ACT (clogged with carbon). I geuss you could confirm the voltage at the TPS, I even found out that my T-stat was faulty trying to solve this problem. good luck keep us posted

[Darren E]

Check your tps voltage when warm sensor could be getting hot and acting up. Also check your o2 sensors one could be shorting out causing it to go full rich at idle dumping too much fuel. Ok under throttle.

[Gallie]

Thanks for all your comments. I'll try what you've recommended.

I replaced both O2 sensors a short time ago hoping it would fix the flashing engine light, but nope. So I'll assume they're OK for now.

What device do you recommend for checking the codes? Where do you buy it?

Thanks.

[95opal]

You can use a paper clip or buy a scanner from here.
http://www.midwayautosupply.com/pc-6...er-cp9015.aspx

[flamed 98 gt]

Have the same problem with mine it was a vacume (sp) problem.

[Dave]

I had an 89GT that would run until it got hot and then shut down until it cooled off( like 2- to 30 minutes later.

If that describes it, Check your TFI Module. It is the grey thig on the side of your distributor with wires comming out of it. They are like 60 bux at the auto parts store, but the trick is getting a tool in there to get it off the distributor. Way back when, ford had a special slim tool to get ot off, I think it is a Torx head.

As soon as I replaced it, it ran fine again.

TFI = Thick Film Integrated

Like you had mentioned, if you keep the RPMs up the car will run, The Module has 2 rpm ranges Low and High.

If the High were to blow out the car would die at High revs, but if the low goes out it just dies until it is cool enough to run, because the module is overheating.

Hope that helps, I worked at a car dealer when I had the problem, and asked one of the techs, and he was like "It's the module" And it was.

Good Luck

[cobraetti]

how do you get that thing off?, anyone

[Dave]

Honestly, I had to mark the distributor, and then turn it so I could get at it. I believe there is a slim socket, that takes the bits for a normal spiner handle or drill, and you get right in there with that thing and it fits.

However it was much easier to put on because i changed the screws to phillips or something.. but then again I owned a hardware store so I had acess to alot of fasteners.

If you get in a hiuge bind, I will try to see if i can find a picture of the extremely tiny ratchet.

I just remembered i think I took it of with a Torx Bit and a pair of alligator vise grips, or needle nose pliers