Solve The Idle Problem From Hell -- Win a Prize!

Have you looked at the BAP/MAP sensors? They allow engine control adjustments based on the weather (i.e. barometric pressure etc.). Have you ever changed the O2 sensors? They may be feeding periodic errors to the ECU. Other things that come to mind are vacuum leaks at various places (although I don't think this is it) like the throttle body/ERG spacer. My money is on a sensor going bad very slowly/intermittently. I'm surprised a code hasn't been tripped though.

Does the car have air condtioning? Does working that control have any effect on the hi idle speed?

Had a similar problem with my 2001 GT but with a twist. Every few months I'd start the car and the idle would stay at about 2500. After the car warmed up a bit, the idle rpm when back down to normal. It happed for about the tenth time and this time the idle didn't return to normal. Took the car to the dealer, and they replaces the idle control valve. All seemed well for a while. A month later, I started the car and the idle dumped. I had to keep it running with my foot. After the car warmed up, it started to idle normally. It did this a few times over a three month period. Then, it happened and the rpm idle didn't come back up. It just dumped every time and I had to keep it going with my foot. Took it back to the dealer and it turned out that the replacement idle control valve was bad too. Replaced it again, and that cleared up the problem. That has been the only problem I've had with my 2001 since I purchased it brand new.

If the dealer cant find anything else and the problem continues, have a look again at the obvious things like the air idle valve. You could have gotten a "putz" replacement part like I did.

Michael

Michael Johnson wrote in news:TP6dnfCYKob9veXanZ2dnUVZ snipped-for-privacy@giganews.com:

smoking.

I'll go with a vacuum leak. Maybe a split in one that doesn't bleed all the time, thus the inconsistency and absence of codes.

Have also solved similar problem by replacing idle air control valve ( intermittent fast idle speeds without setting any trouble codes);

This is typical with a car that is 15+ years old. There are so many components that just wear out and are hard to identify when they do. The Fox cars have just enough electronics with poor diagnostics to make them a pain for us old school mechanics.

VLeaks - check the little rubber elbow at the gas fume canister, front engine bay, lower, passenger side, they expand and get too loose, almost fall off, no replacement available, got to roll your own.

Clean the injectors ? (long shot)

replace distributor cap, (shorts on inside of cap) replace rotor too.......

the O2 sensors get "lazy" after long time

you could have a wiring problem, somewhere (like that helps!)

Seems like something is intermittent in open loop.

Let us know what you find,

thanks

-87 5.0

-93 5.0 8# KB

Even though you already replaced it, replace the IAV again, as one of the other poster mentioned. If you want to mess around before doing that you might also try readjusting the idle speed. I replaced the IAV on my 88 and it still had a lot of fluctuation until I adjusted it as follows...

Engine off, back out the idle stop screw till it no longer even touches the lever. Then screw it in to the point where is just barely touches the lever and then give it an additional quarter turn. Then try driving the car and see if things improve. If that doesn't work, give it another quarter turn in and try again. If that doesn't work, buy a new IACV.

Have seen the same in a Jeep, sticking idle air control valve... dirt/carbon buildup caused it to stick intermittently. Weird thing is, resetting the ECU always made it work ok for a short while. (disconnect battery cables). I guess the ECU re-read all sensors once and adjusted to the prevailing conditions (open valve)

Jan

Ashton Crusher wrote in news: snipped-for-privacy@4ax.com:

If the idle stop screw was never touched in the first place, I'd stay away from it. Changing it might compound the problem, making diagnosis even more difficult.

true.

I would also clean (inside) just behind the throttle valve itself, I found a rim of carbon built up behind it from the manifold exhaust that is fed back into the intake, which was sticky.

If you have run out of other options, try tracing down the ground wires for each sensor, but particularly the ECU and make sure that they are clean underneath to frame. Also look at any splices that are inline as a bad crimp can do most of what you describe.

cheers, chuck...

It's not rocket science. If that's a concern a person can always count the turns so they can put it back just exactly where it was.

Ashton Crusher wrote in news: snipped-for-privacy@4ax.com:

performs

driving/

helped/worked.

diagnosis

Still, no reason at all to change it if it's never been touched. It's obviously not the problem.

Well, the original parts of any sort were never "touched" so I guess there's no reason to replace or adjust anything to solve the problem, just call in someone with chicken bones to say a chant over it.

Ashton Crusher wrote in news: snipped-for-privacy@4ax.com:

somewhere

adjusted

Time plays a factor in a lot of problems, e.g., sensors wearing out or getting dirty, vacuum hoses splitting, etc. Throttle stop screw isn't one of them.

And you know his has not backed out because???? Or that it was not improperly set at the factory because???

Sounds like a possible bad wire (shorted) going to the AIR IDLE solenoid.

Ashton Crusher wrote in news: snipped-for-privacy@4ax.com:

I doubt Patrick would've messed with it in the first place. And IIRC, those screws had a factory plastic seal (or something similar) around them to discourage tampering.

The car had been running fine until recently.