Engine running rough while idling

[tiffytime]

2002 Chevy Trailblazer running rough when idling, especially when its cold and it sometimes hesitates. The engine sounds like it is missing. Thought it was because I got some bad gas but still having the problem.I have replaced the fuel filter, spark plugs, ignition coil #2,4,and 6 and 2yrs ago the throttle position sensor. When i replace the fuel filter i notice the gas that came out of it was very dirty. I have also used the fuel injector cleaner a few times when I filled up with gas.What else could be making my engine run rough?

[maxwedge]

Welcome to AF, no codes or check engine lite? Rough is vague, is this a misfire how is it under load say in o/d at 50 up?

[tiffytime]

No codes came up and check engine light didnt come on. The running rough is a misfire. I'm not sure what you mean by o/d? Perhaps overdrive. Over 50mph it runs okay, seems to be lacking pep in acceleration.

[maxwedge]

Yes under load in overdrive, anyway a scan looking at misfire counts should point to the suspect cylinder, ,bad plug, coil, injector,or low compression in that cylinder are all in the mix.