We just bought an 05 Cavalier and about 3 days after we bought it the check engine came on and it was idling weird. I replaced the plugs with some cheap ones and it ran fine for about a week then it came on again and wouldn't hardly run. The g/f ran the codes and it was a misfire just not sure which cylinders. I went and replaced the plugs with AC delco OEM plugs and the car has ran fine for a couple weeks. Today it threw code P0301 cylinder 1 misfire. I'm not familiar with these cars so I'm unsure what to check now.

If you have a buddy with a Eco, swap the black pieces ontop of the engine, there your coil pack and ignition module. Those usually go bad, and cause this problem. If it goes away with the one from another car, great if not, then check the injectors, but im willing to bet money its the coil pack/ignition module. Goodluck!

Thanks for the response, that is kind of what I am thinking now. Last night i brought the car home and just unhooked the battery and the plug that when to the coil pack, let it set about 30 secs and plugged it all back in and no more missing.

Hmm, never knew you could reset the module like that. But none the less, glad it worked!! But come to think about it, the plug going into the coil pack could have been loose, and when u replugged it in caused the problem to go away. Hmm.