Rough idle

My '02 trailblazer with 92,000 miles has been idleing rough and vibrating and I changed out the spark plugs. three of the plugs had oil on them. After changing the plugs the problem still exists. I am now getting a service engine soon light where I didn't before. Has anyone had this problem before? What is it and how much am I looking at in repairs?

Not enough info to really help here, get the codes read and post back.

I would check for carbon tracks along the plug wires and boots. I have to have the boots replaced on one coil because of that. Easier to see arcing at night.

Can't do this on the TB the coil covers the boot and the plug, maybe you may see the coil arc over, but unlikely.

Had this happen to me ... and just noticed it again in the past couple of days. About 2 years ago, before my ext. warranty ran out, the dealer cleaned my injectors. Since then, I've had to replace the injectors...yes replaced them. (it's been a while...so I'm not sure if replacing my injectors had to deal with the rough idel or not.) My mechanic did this for me. I do know that the gasket was leaking oil on them. We're keeping a close eye on things right now, and he suggested that we may need to clean then annually. Anyone have other suggestions?

P.S. My TB is an '02 LS with 104,000 mi's on it. Nice to see someone else drives their vehicle about as much as I do.

I would try a complete throttle body cleaning, IE, taking it completely off the truck and spraying it down with a good cleaner. You'd be suprised by the amount of gunk on the back side of the throttle plate. To get the full benefit from this, have both battery terminals disconnected while you do this. I did mine for a slight stumble off the line, seemed to help. I didnot however disconnect the battery terminals.....which I will be doing tomorrow, they prolly need cleaned too anyway. It's worth a try, it's easy, & you're only out the price you pay for the cleaner.

i agree on the throttlebody cleaning. its a common problem on our SUVs. i had mine cleaned before warranty ran out. service department wrote that it was extremely dirty.

My '02 trailblazer with 92,000 miles has been idleing rough and vibrating and I changed out the spark plugs. three of the plugs had oil on them. After changing the plugs the problem still exists. I am now getting a service engine soon light where I didn't before. Has anyone had this problem before? What is it and how much am I looking at in repairs?


Hi i have a similar problem were my truck idles hard, I also change spark plugs and spark plug boots which i was told by the dealer and i still have the problem. Im going to check my fuel injectors cause that would also cause the truck to shake.

Had this happen to me ... and just noticed it again in the past couple of days. About 2 years ago, before my ext. warranty ran out, the dealer cleaned my injectors. Since then, I've had to replace the injectors...yes replaced them. (it's been a while...so I'm not sure if replacing my injectors had to deal with the rough idel or not.) My mechanic did this for me. I do know that the gasket was leaking oil on them. We're keeping a close eye on things right now, and he suggested that we may need to clean then annually. Anyone have other suggestions?

After changing your fuel injectors does your truck still idle rough cause thats my next step and is it expensive.