2003 cavalier rough idle

SOURCE: 1998 Cavalier No Spark in cylinders 1 & 4

ignition mod. grounds,pcm or timing belt could all be it but, I would have to look at timing first.

SOURCE: 1999 Z24 runs rough when warm

Buy a couple bottles of gas line antifreeze.... the coil would have been my first suggestion... but it sounds like you have water in your gas as well.... gas line antifreeze is alcohol (not the kind you drink) it sucks up water tho.

Robert

SOURCE: 1998 Cavalier Quad 4 2.4l runs rich wont rev past 1500 rpm

can be a mass air flow, idle air flow ,or even a hole in the tube between the airbox and the throttlebody........any air leak will cause this to happen.make sure you have no vaccuume lines off either

SOURCE: 2001 Chevy Cavalier Misfire

Have you made sure your getting spark on every cylinder from the coil pack?

SOURCE: I have a 1997 Chevy Cavalier with a 2.2 Liter

This sounds like a classic fuel system problem. Manually check your 1 & 3 plugs to prove /disprove the code. If they're OK, which I'll bet they are, check the fuel pump. If it tests good then you have a fouled gas tank, I'll bet. Especially if you live in the Northwest. If you let it sit with low fuel, the extra air space lets condensation form, causing rust and moisture in your gas. Usually changing the fuel filter will give you some temporory improvement if this is the problem. If it didn't then it could be your air intake not delivering enough flow to give it the proper fuel/air ratio. When's the last time you changed the air filter?

Testimonial: "Helped me rule out the fuel system."