OK so the ACdelco plugs have a rebate of $2 back right now and my truck has 95,000 miles so I changed the plugs. There was nothing wrong with my truck before.

Now my truck has a strange Idle bump every so often. The engine runs slightly smoother but when im at idle I will feel a bump......bump.............bump. Sometimes I dont feel it until I put the AC on and the truck in drive. Its like the slight load makes the idle drop and it miss fires. I dont know.

So here is what I have done so far. I have cleaned the MAF sensor. I have cleaned the throttle body and I had run a bottle of Techron through it before I changed the plugs even. Now its on its second tank of techron.

Any Ideas? Its not the head issue cause mine was replaced in 2009 and this has started right after I changed those plugs. What should I do next? Should I just drive it a few hundred miles and see if the computer adjusts to the plugs or something? How would I know if its a coil?

 

[QUOTEThere was nothing wrong with my truck before.][/QUOTE]

?? you could go back one step,put old plugs back. if its good then, take new plugs back.

the more cleaning,other stuff you do to cover it up will complicate the sorting out process.

did you disturb hoses/other stuff while doing plugs?

 

I am going to remove the plugs and check them out later today. The only thing I can think of is maybe a coil is not on right. Is there something I didnt do? I've never seen this coil on plug kind of setup and I just screwed them right back on.

 

me,never did it,just going by what others said. could be a crooked coil??
ive never seen one in person!!

 

If the only change made was installing new plugs, look there for the cause. Like DrTom says, changing unrelated things only complicates troubleshooting. 95% chance its in the engine ignition circuit...something you handled. Tracking down a light intermittent miss can drive you nuts.

Its most likely a shaky connection or old plug wire that is broke down from after some handling. Carbon plug wire breaks down with age. I'd recheck each step, especially the snugness on all the connectors. If they're good, turn off the garage lights and watch for arcing from the ignition leads. Check the continuity of each plug lead. It could be a bad new plug; it happens. Did you check the new plug gaps? A bad gap could result in an intermittent weak spark. If its a steady miss, you can get a spark test light for a few bucks that goes between the lead and plug to show if its firing.

 

The I5s have no plug wires and no place for an arch from an ignition lead?

 

No tricks, super easy. When you place the coil on plug pack back on the new spark plug, you have to put it back on the plug like a regular spark plug boot. Make sure the plug goes in the boot and the boot is all the way down and centered on the plug, then tighten the retaining bolt.

The contact with the plug is made by a spring under the coil to the plug, if it is crooked, or the plug insulator boot is hung up, it might be a bad connection and cause a miss.

Good luck.

 

Oops. I got the idea somewhere it was a 5.3.

 

I fixed it. Horrible horrible expierence. The truck only got worst lots of rumbling and misfires. Check engine light of course came on and I limped back home. I took out the plugs and went over the installation again. Still had the same results. Then I went to the store and purchased champion double platinum plugs. I put them in and the trucks running great. I compared the champion plugs to the ACdelco and the gap was nearly the same so I didnt gap them. The only thing I really noticed different is that the champion plugs are a little longer. I dont know what to tell you guys.

Perhaps the 2006 hummers dont like the new model acdelco plugs? My old plugs werent even giving me any problems. I wonder if I can get a refund???

 

Also the champions called for a 0.60 gap on the computer. This seemed way off so I paid no attention to that.