1992 Pontiac Firebird

Maintenance/Repairs
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1

I have been having some recent issues with my 92 bird lately. It started minor but now

the car will not stay on. It originally started out as I would need to press the gas to get it

to start and it would stay on, but now if I let my foot off the gas for anything it will just

idle rough and die out. I took it into a shop and they said that I had a bad idle control

valve and the pigtails need to be replaced. They also said that some wires were shorted

out and they would replace those as well. They replaced the Pigtails and the idle control

valve and the car started to work fine again, for about 4 days only. I drove to the store

and when I came back out to start it back up it wouldn’t stay on unless I gave it gas. I had

to drive it home giving it gas and using my other foot on the brake so that it didn’t due

out. I checked the job they did and doesn’t even look like they did what they said they

did. I looked at the botched shrink tube job they did and it just doesn’t look that

professionally done. I did call the guy and he gave me an excuse and said that they short

must have traveled further and he was surprised that the car was even running when they

were done. I of course just hung up the phone after hearing that. I did a little looking

around the engine and I noticed that if you unplug a vacuum tube and press on the gas

and hold it at 2000 rpm for a few seconds and let off the car will stay on, but the moment

I plug that hose back up with my finger or plug it back in the tube slot, the car idles rough

for a few moments and dies. Can anyone give me any advice on what I should do or

know of a fix???

2

Your idle air control valve is still screwed up. When you open a vacuum port, enough air leaks in to keep it running. close it and it dies. The IAC lets a little air in and the computer tells it how much to open or close to keep the idle at the right spot. Take it to a new mechanic and tell him what your wrote here. The earlier fixed worked for 4 days, sounds like the wires weren’t properly spliced and are no longer making contact.

3

I was thinking that maybe the idle control valve they put in wasnt doing its job. They said they put a 130.00 part in straight from GM. I know this shop gets all their parts from napa, so I doubt they contacted GM and had them send a part right over.

4

A vacuum leak can cause all kinds of idle problems and even mimic an IAC fault.

I have no idea what this hose you’re referring to could be without knowing what engine you have and without some clear pictures of it but maybe it’s related to the EGR system.
If the EGR is stuck open for whatever reason an engine will idle rough or not at all and the EGR itself is a vacuum leak. However, it’s a controlled one when things are as the should be.

5

I should add that my engine is a 5.0 V8 with OHV. I forgot to put that in my post. I also like to mention that the hose that I unplugged runs to the throttle body from the Air Temp Sensor. Im pretty sure that I can unplug any hose that is connected to the throttle body and I will get the same result.

6

There are usually a host of things that will cause the engine rpm to increase. Turning on the headlights, turning on the rear window defroster, turning the steering wheel (if power steering), the engine radiator fan turns on. Do a little research and find out what these things are for your car, then see if doing any of them fails to increase the idle speed. Does the car idle faster when you first start it with the coolant cold, then the idle rpm gradually slows so that after 2-3 minutes of idling the idle rpms slows to normal? If not, could be a clue.

If this were my car the first thing I’d do is test each and every vacuum controlled device for potential vacuum leaks. Esp if this happened suddenly, one day is was idling fine, and the next day it wasn’t. After that I’d do an EGR test to make sure when the EGR vacuum is applied, it noticabley degrades the idle or stalls the engine…

7

The short moved up the line is the funniest (and stupidest) excuse I ever heard from a mechanic.