Ok I'm new to the board so hello to everyone nice to meet you.this my second cobalt and I'm very happy with it. It's a 2008 ss tc I bought not that long ago and it ran fine started to throw a p0300 code so I changed plugs out for e3s code went away ran fine for a lil . now it has a real rough idol the rpms don't bounce that bad but feels like it trying to stall. It also throws p0300 through p0304 codes under wot. It sounds like popcorn and loss of power. You can feel it missing under light throttle but its not that bad enough to throw code till about 4k rpms and past. I'm worried because I can't seem to find the solution. Took it to dealership and they said that they have to go into the computer and have their mechanic chang stuff to start to find the problem they said it could take up to a month. Car has injen cold and hot charge pipes and some kind of tune its at 20psi before all this it ran really good. Please help

 

Sounds like it could still be the spark plugs... did you pull them again and see how they look? How long have you ran the new set in? and what kind... perhaps you're not running the right ones.

Who tuned it?

 

Get those e3 plugs out and put stock ACDelco plugs in. The LNF is picky

 

Not sure who tuned it and plugs look okay

 

stock ones do the same thing

 

Jesus christ man can you make a few more repeat threads?