I have an 1989 GMC JImmy.
Has horrible stuttering and I am going to replace the plugs and wire. When its not to damp it run great. When its raining like mad its just HORRIBLE to drive.
I had the same problem with my 1990 Sierra 5.0L. It ran OK in dry warm weather, but in cold and damp weather it would backfire, miss, and almost stall if I stepped on the gas too hard. The problem usually corrected once the engine ran for about 15 - 30 minutes, although I still could hear it missing at idle. I tried new spark plugs which helped a little, but the problem was still there.
Finally we decided to change the distributor cap and rotor, which cost about $25. The problem went away instantly, as it was a rainy day when I bought the new cap and switched it. This is definitely something to try. I also noticed a dramatic improvement in gas mileage.
We just bought a 1989 GMC Sierra from my father in law and are hoping to use it to tow a trailer.
Does anyone know what the towing capacity is- or where to find it? We called GM and they have no idea (very helpful!!)
My dad gave me his 89 extended cab 5.0 and its got 213,000 miles on it is there a club for GMC's with over 200,000 miles also I have the same stuttering problem, I'll change the rotor and go from there email me about a 200,000 mile club@ firstname.lastname@example.org.
I had an '89 Chevy Cheyenne 1/2 ton pickup truck that had a stalling problem, and it turned out that the fuel filter and the fuel pump sock were completely plugged up. Hard to believe that it could actually run like that. Once all that was sorted out, it ran like a dream and never complained again.
Alright guys. I just bought a 89 2500 with the same stuttering issue. It's the gas cap. When it wears out it won't vent and causes the problem. Replace the cap... Problem solved. To easy. I just hope you GM fans out there didn't spend a small fortune replacing parts that weren't the problem. Hope this helps. Fixed my issue right off.
Check to see if water has been getting under the hood via the windshield. If so, check under the distributor cap for rusty parts. This model is notorious for this. If it's rusty, replace it. If it's not bad, it will be soon, and you'll save a headache.
Next, start the engine while cold (have a fire extinguisher handy) and spray carb cleaner on all vacuum fittings. Listen for changes in the engine. A good place is right in front of the throttle body. Three fittings get a lot of thermal abuse there. EGR and PCV valves need to be checked after that. Then you're on your own. Those are the typical problems.