Saturday, July 16th, 2011 AT 3:35 PM
I have a 1999 gmc ext. Cab siera w/5.3 L, w/ 190,000ml and it runs good it dont miss fire or run rought, But when I turn the air or heat on it starts to run rough almost like its miss-firing and when I take off from a stand still it hesitates and when I turn it off it goes away and plugs are under a year old.
