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1992 GP Won't Idle


Marken
04-19-2010, 07:54 PM
I hope someone can help. It's driving me nuts!

1992 GP with a 3.1. The problem started in November. The wife filled up the car with gas and on the way home it just died while going down the highway. She got it pulled over and it started right up but would hardly idle. It would surge. This happened three times while coming home.

I checked everything I could and found nothing. Took it out for a ride and while coming to a stop it just quit. I finally ended up draining half the gas out and put some other gas in and it ran fine.

Fast forward to this month and it started doing it again. Whenever she would come to a stop the car would just shut-off. It would start right up but she had to keep her foot on the gas so it would idle. Well, one morning she tried to start it and it wouldn't start. I finally went out and I got it running if I stepped down on the gas pedal while starting it. The minute you let off it would die.

I had to turn up the idle screw to keep it running and finally took it to a garage for repair. When I filled it up with gas this time it didn't help. They first did the diagnostic but no codes came up. Then they started replacing parts.

Idle air sensor
MAF sensor
O2 sensor
Computer
TPS

Problem still remains, but it will idle, although rough. What I noticed is there is no fast idle now when started when cold and it surges. When warmed up it will idle a little more smooth, but still stalls. Runs great at highway speeds, but not when you try and come to a stop.

Any suggestions? If you need more info just ask.

Thanks for any replies.

Ken

mechanic1980
04-19-2010, 08:23 PM
i would try a fuel filter and check the intake for a leak

doctorhrdware
04-19-2010, 08:57 PM
I would check your fuel pressure and the fuel pressure regulator. Pull off the vacuum line and check to see if there is fuel. If there is replace the regulator.

tblake
04-20-2010, 09:07 AM
Ohm check the injectors. It will be sort of a pian because you have to remove the upper intake. But you could probably just unbolt it and angle it upwards. Be sure to replace the gaskets. The injectors are batch fired on this car meaning if one is shorted out, all the current for that bank of injectors will flow through the shorted injector and not fire the others. Look for approximately 12ohms on each injector. A little higher is fine, but if you have any less than 12, I would be concerned.

Marken
04-20-2010, 12:28 PM
Thanks for the replies.

So, your thinking it's more of a fuel delivery problem than an electronics issue. What if the injectors check out and the fuel filter is good? Is there any way to check if one or more of the injectors are plugged? Could that also be a cause?

We've had it back in the shop three times. He keeps on adjusting the TPS which really makes no difference.

tblake
04-20-2010, 08:50 PM
I didn't think there was a way to adjust the TPS on that motor. To clarify you have a 3.1mpfi or a 3100sfi? Have him check fuel pressure to make sure it holds, and then if all the injectors ohm out correctly, I would have the shop do an injector balance test which would tell you if all injectors are spraying.

richtazz
04-21-2010, 07:46 AM
I agree with Tim that checking fuel pressure, both key on/ engine off and while idling with both vacuum attached and disconnected is our first step here. It's the easiest to do as you have to remove the upper plenum to check the injectors (which is the next thing I would do if fuel pressure checks out).

Marken
04-21-2010, 09:00 PM
Yes, it is a 3.1mpfi.

Car is going back in Friday. I'll have a little chat with him about what you suggested.

Thanks for the help. I'll let you know what happens.

Marken
04-26-2010, 08:45 PM
Here is the latest.

Took the car in Thursday night. They pulled it into the garage and disconnected the battery. Wanted to reset the computer.

Hooked it back up and they got an error code. Bad idle air sensor. Third one! Replaced it along with a bad temp sensor, reset the idle and we picked it up around noon on Friday.

Wife said it ran much better but the temp gauge was hovering around 220. I checked the coolant (full) and made sure the cooling fan was coming on. Next morning she took it to town, or tried to. As she was driving down the highway all the dash lights came on and the temp gauge was heading towards 260. She pulled it over, it stumbled and died.

When I got there, she took the truck home and I took the car back to the garage. The dash looked like a Christmas tree...every light was on and it ran like crap. Temp was back down to almost 220.

Called this morning. Another bad idle air sensor and they thought the thermostat was bad. Didn't figure out what's up with all the lights though.
Said I should call back tomorrow morning.

And this saga continues...:headshake

richtazz
04-27-2010, 04:01 PM
I see the ECM was replaced. Check to see if it is a Cardone branded reman unit. These are a high failure rate brand and it sounds like another bad ECM with all the dash lights coming on. Also check the vehicle harnesses to the ECM to insure that none of the pins are bent, broken off, or corroded. Lastly, also check the underhood fuse and relay center for corrosion on the underside since I see you live in Wisconsin where they use plenty of salt on the roads in the winter (right Tim?).

doctorhrdware
04-27-2010, 09:49 PM
In WI even more then IL. That is why I do not travel north in the winter.

tblake
04-28-2010, 09:45 AM
Don't get me started on rust.....

Marken
05-31-2010, 10:23 PM
Well, I'm back:frown:

It's been a month. Last time the car was in the shop they replaced the ECM again along with the idle air sensor. Car ran fine (except the gas mileage went down to about 26mpg) up until Thursday. When I started it it acted like it was flooded. Had to hold the gas pedal halfway down or it would die. Ran like that for almost 2 minutes before it just cleared up.

Was on the way home when it started acting the same way while going down the highway. Lasted for about a mile and then cleared up. Went about 4 miles more, the car jerked and just died. Put it in neutral while coasting and it started right up and made it home. CEL came on both times.

They insist it's not a fuel delivery problem. I'm not so sure. Taking it back to the garage in the morning. I'm curious what the error code is this time.

Wisconsin uses the 1-1 rule. 1" snow = 1" salt:smokin:

richtazz
06-01-2010, 08:26 AM
you can pull the error codes yourself with a paperclip if you don't want to pay a garage. Here's a link on how to do it.

http://www.troublecodes.net/GM/

Marken
06-01-2010, 05:42 PM
Thanks for the link, but they don't charge me for the service.

Error code that came up was the ignition module. Could it also be the cause of the drop in mpg?

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