I have a 1990 GMC K1500, stalling issues.

Asked by campjl57 Dec 01, 2012 at 07:30 PM about the 1990 GMC Sierra C/K 1500

Question type: Maintenance & Repair

the truck will start up most time fine with a little gas, after about 30 seconds in idle it will do an
irregular idle and then stall out. Also when I put the truck into reverse or drive without my foot on the
gas pedal it will stall out. I can drive the truck as long as my foot is on the pedal giving it a little gas
when I'm at a stop light.
So far I have replace the IAC, PT sensor, ECS module, Ignition module, spark plugs, distributor cap and
wires, fuel pump relay, fuel filter, i have cleaned the carburetor with cleaner spray.Please help!!

32 Answers


Have you tested the fuel pressure? Sounds like the pump is dying.

So, I changed my fuel filter again and it's running much better but is still stalling, I haven't done a fuel pressure test yet but while I was under changing the fuel filter I saw a pretty major exhaust crack. Do you think this has something to do with the symptoms?


If the exhaust was bent I'd say yea but no not a hole. I'm still betting on the pump.


Bloomington ca.... I have a 90 GMC 1500 5.7 have almost the same problems i dont have the same problem but i dont need to keep my foot on the peddle when you punch it too fast the idle drops and stalls cause its in a high idle i have everything brand new but the fuel pump i was told that it could be the computer i replaced it and its still doing the same thing i took it the mechanic and he had it on computers i was told it was the transmission can i took it to the transmission shop and its okay i was told it could be the wire harness it could be a short so i look at it and still havent found anything yet.... im still stuck on it im getting ready to get rid of the truck!!!

6 people found this helpful.

What is your fuel pumps pressure

2 people found this helpful.

same here, but my fuel shoots 6 to 8 inches across intake when pump is running. i tried this when throttle body was off. i just replaced fuel pump, fuel filter, new injectors, computer, coil, alt, egr valve, checked every vacuum line and intake for leaks, and it idles fine but soon as rpm gets about 1500 it cuts out really bad and if i floor it it will surge from barely running to high rpm. i cant drive over 35 mph. and would a mufflef that has a bend sideways in it cause this?

3 people found this helpful.

Yes a bent exhaust will act exactly like a clogged catalytic converter, light throttle at low rpm is fine but full throttle or higher rpm and the engine can't exhale, it's like trying to hold your breath and suck in more air, eventually you won't have room for more air in your lungs and you can't hold your breath forever. Just unbolt the exhaust and see if it solves your problem.

2 people found this helpful.

An engine under a heavy load consumes about 50% more air than it would in neutral being revved.

2 people found this helpful.

now when i wiggle the wiring harness going from inner firewall to computer it stops acting bad for a second, but returns back, i have checked every wire in the harness and found no cracks or any broken or frayed wires. all the plugs look good and hold tight, could it be a bad ground somewhere

4 people found this helpful.

You may not see a fault in the wire but it could still be there, I spent quite some time chasing down a bad wire for the ac compressor. Found a hunk of wire that had corroded from the inside, not sure if the wire was nicked or if it got moisture in it when it was made but there was about a quarter inch of the inside that was just a green/white clump of dust. Couldn't find anything wrong with the insulation.

1 people found this helpful.

My 1990 GMC Sierra Single Cab 350 Throttle Body Engine is giving me fits!! At random times the engine just stalls out and it will not start back up for about 45mins to an hour. Afterwards it goes back to running great. The Mechanic stated the Check Engine Light stated bad fuel sensor so that's changed and all electrical components have been changed (Distributor Cap, Rotor, Wires, Spark Plugs etc). Please Help. I get embarrassed broke down in the middle of the street. Thanks.

10 people found this helpful.

You replace the fuel filter? Fuel filters are notorious for getting clogged, stopping the engine, sitting for a while allowing the sediment to settle, and then starting back up like nothing is wrong then running until it clogs again from the debris stirring back up.

3 people found this helpful.
Best Answer Mark helpful

Camp you find out what was wrong with yours?

1 people found this helpful.

Fuel pump was spot on. I have another issue with the breaking of my truck. It take for ever to stop. It will not come to a screeching halt and it's a bit dangerous if someone did know how horrible the breaks were. ( I have to stay back a good distance for room) the break pads are good I was wondering if 1990 gmc just have crap breaks to begin with or if there's something I can check or do to improve this problem. -JC


no, i've had plenty that stop great. Is your ABS activating prematurly? You can feel the pedal pulsating when it does. I had that happen before. Other than that you need to make sure the rear drums are adjusted properly and bleed everything out. Ensure neither of the calipers are stuck

1 people found this helpful.

Yea do what Andrew said also check the rubber lines while someone presses the brake pedal, a swelling/stretching line could reduce the amount of potential pressure resulting in what would seem like a light pedal application could also be a worn master cylinder but I wouldn't go for replacing that until you have definitely ruled everything out.

2 people found this helpful.

on the 5.7 that wont stay running if the temperature sending unit is bad then the truck will not run right or get the right fuel mileage it's located on the housing for the thermostat. there are two of them one is for the gauge and it's on the left head right behind that first plug the other is for the computer

3 people found this helpful.

Greg , if tsi to comp is bad will it prevent the engine from starting ?


my truck seems like once it warms up it doesn't idle high enough the oil pressure drops and if I don't keep my foot on the gas it will stall out.

7 people found this helpful.

I had to replace my gas pump and it fixed the idle problem.


i have a 1990 sl sierra gmc1500 and wires are disconnected on the distributor also non of the plugs fit it how can i connect the distributor so i can get the truck running. the person that was working got paid but never fished the job.

2 people found this helpful.

If the connectors won't fit you have the wrong distributor


I have some of the same issue stalls when I take my Foot off of the gas pedal also have transmission shifting problems. Some history I just bought the truck everything was good except the front suspension. But it has been setting for 5 years. I pulled the bed and replaced the fuel pump complete unit with sender, fuel filter, there was about 5 gal of gas in tank I put 5 more gal in it looked clean when I had sender out so I did not replace the fuel. I did put some aditive in the fuel, replace, distributer cap and rotor. Is there a way to clean the TBI system could that be my problem? The Trans mission will not shift unless you have the rpms high and let off of the excelerator and then it does not always shift. Changed filter and fluid. Should I try changing the filter and fluid again? Is there a way to back flush it, will it get better after I run it, any ideas? Thanks

2 people found this helpful.

Ok I had the same problem just figured out what it was. Those little plastic caps with the wires going into them some times those come loose and they don't send the signal to put gas in the engine. Sorry they are on top of the fuel injectors. Pop your hood and let it idle make sure you are getting gas to your engine.

1 people found this helpful.

Also check your throttle positioning sensor it sits under your air intake.

I have a 1990 GMC Sierra and my idle did the same thing! I have a new crate motor in my truck and replaced the entire fuel system and injectors and still had the same problem. I found a short in the wiring harness going to my TPS sensor and once I fixed the short and replaced my TPS my idle is perfect and I haven't had any problems with it since and it's been about a month

I also had this problem had to replace throttle body gasket fixed the problem the brakes were going to the floor it was the rear brake shoes one of the spring pins came out due to the c clip popping off that held it now no reverse its a 1990 Cheyenne in very well kept condition just going to get another tranny from the self serve yard been having good luck there its about the only place you can go on a budget they have online coupons and factory parts plus for a few more dollars they give a year warranty and I have never been unlucky so far there so ill take a chance got nothing to lose

I have a 1990 GMC 1500 and had a high idle changed throttle body gasket and fixed it right up. Then it started running a little ruff when I would get on it the truck acted like it wanted to skip took it to a guy he had it about a month he never figured it out so I replaced the plugs and wires distributor cap and rotor button and it got much better. 4 or 5 months later it was doing the same thing I left the house drove about 4 miles and back and now it wouldn't go into passing gear well when I got back home cut the truck off went inside and right back out and truck turns over fine but it was dead with no spark at all. Advance auto said the pick up sensor was bad so I bought a new one also the cap and button didn't look to good and the top of rotor button was like burnt on the top. After replacing all that still no fire so I bought a new coil and no fire. I'm no macanic but know enough to be dangerous but I got brave and marked the base of the distributor and where the rotor button was pointing and pulled the whole distributor out and when I would turn the gear it didn't want to spin very smooth so I got a pull apart used one and put the pick up on it dropped it in on my marks put it all back together and now she is running like a new one.. Hope this may help someone else out because it about drove me crazy..

Check your ignition control module, it's a little guy that everyone seems to over look, it could be the source of your problems

I have the same problem with stalling on my 1990 throttle body Chevy Silverado 350 engine. I have a fairly new Jasper engine, new throttle body and cable, new distributor, and constantly going to repair shops. The engine will lunge and slow, lunge then slow. Stops in the middle of intersections! Do I need a new computer? How do you get one before 1999? My mechanic did not undo the black and brown wire before setting it OFF of top dead center video shows that being done. He said the computer corrects anyway. anybody want to buy a neat truck?

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