Rough idle
 

I'm still a Newbe so I will appreciate any help I receive and Y'all have been VERY helpful in the past. I changed spark plugs about 3500 miles ago with 104,000 miles showing on my 08 Panel LS and no issues. Friday I start her up and it is missing/idleing rough. A lil peddle and all is good, back to ilde and miss/rough like I am dropping a cylinder. I am on the road A LOT for work and fueled up in a station I've not used before but was very busy so I assumed fuel was fresh. I have not tried any additives, seafoam, drygas or injector cleaner of any kind. I am not sure exactly where to start? No check engine light and I do not have a code reader.....YET. Can you help a guy out who spends way to much time on the road and depends totally on his HHR to do him right.

P.S. I do know my way around the enginge compartment and can turn a wrench or 2 but everyone needs help now and then

What plugs did you use first off? if you use the ac delco stock plugs hope you did not gap them just put them in no gap need... It would be wise to throw injection cleaner with 110,000 miles seafoam or techron good stuff .. good luck

The "classic" answer to rough idle is: dirty throttle body.

Although the check engine light is not on there still may be a code in the system to help you figure out where to start. If your local part store can read codes have it done and tell them to look for pending codes. Pending codes are the same as the trouble codes it's just has not turned on the check engine light.