GMC Other

1999 GMC Yuckon Denali 145,000miles. It has a 5.7L vortec engine. I notice a rough vibration when idling. It isn't something big just something I notice a lot. I recently replaced The TP sensor, Spark Plugs, Spark Plug wires, Fuel Filter, Air Filter and serpentine belt. I just want it to idle nice and smooth. I am thinking it might be the Vehicles timing but don't want to waist all the money if it ain't the problem. I was wondering if there is anything else I can do to get rid of this rough/poor idle? When I replaced the spark plugs I noticed that one of my plugs had oil around the threads Is this something to worry about I checked my oil and noticed that it was low. What could this problem be?
June 29, 2006.

Hi, you mentioned oil around the threads of a spark plug. Since you have changed the plugs with new ones, go back out and removed the one that was oily. Is it still oily? If so you will be experiencing lower compression in that cylander hence the rough vibration.
Do not for any reason try to adjust your timing unless you have the proper tools and instructions on how to do it. Your on-board computer monitors and manages the timing of your engine.

Aug 12, 2006.