2003 gmc sierra denali

[Robertl]

does anyone know why a truck would run rough after having a tuneup. the thing runs very rough while in gear at an idle. all plugs and were replaces and emission cleaned with new fuel filter. the truck is at 160kkk miles. always changed oil at 3000 miles or so and not a towing vehicle. at least since i have owned it in 4 years. if anyone can give me a idea as too why or possible reasons as too why. thanks

 

[Molson02536]

does anyone know why a truck would run rough after having a tuneup. the thing runs very rough while in gear at an idle. all plugs and were replaces and emission cleaned with new fuel filter. the truck is at 160kkk miles. always changed oil at 3000 miles or so and not a towing vehicle. at least since i have owned it in 4 years. if anyone can give me a idea as too why or possible reasons as too why. thanks

Could be lots of things, first would be to check the spark plug wires . The wires could even have been re-routed that it's to close to the exhaust manifold and has burnt through and there is grounding. Is there any check engine light on the dash????

Without knowing much to what was done for a tune up, everything is just a shot in the dark to why its running ruff for now. Start with the simple and recheck the spark plug wires for damages and i they are in proper firing order.

keep us posed and good luck.

Molson02536

 

[Robertl]

tks for replying

the tuneup was plugs emisson cleaning and fuel filter the 6.0 ltr has something called coil wires or ???. the check engine lite is not on?? i checked wires and none are bad or disconnected.the feeling i get when its backing up is that its loaded up or running rough. never had this problem before tuneup???? thats whats so questionable. I hate too put blame on anyone without proof but the thing never had any issue before. i was just doing the required maintenance according too the manual..

 

[Denalibob]

I had the same issue with my car and it turned out to be 2 bad ignition coils, easy to replace. Have your coils metered for resistance to detrmine the bad ones.

 

[The Kid]

Personally I would start looking for a loose connection of one of the coil packs. The guy who tuned it up might not have snapped them back correctly. It might have run good in the shop but once heat builds up under the hood then a connection is lost. Same with the injectors. Look to make sure everything is properly plugged in. I can't believe a repair shop would turn over a vehicle back to the owner with a miss in it. Get a bright flashlight and go hunting. -kid