I had the exact same problem. Code 404, the egr valve that sits above the exhaust manifold. My mechanic told me either to replace the egr valve or let it go, since the CHECK engine light comes and goes periodically. When it is off, everything is fine the car runs great. Then, the engine will start to misfire, followed by the CHECK engine light at the code 404. My mechanic says sometimes pieces of carbon will come off from inside the exhaust manifold causing the EGR to stick. So when it works again, it "fixes itself" by the piece coming free from normal use. The mechanic says when you put fuel injector cleaner inside it sometimes causes junk inside the engine to float away and sometimes it gets stuck inside the EGR causing the code and misfire, plus the CHECK engine light coming on.
For now, I am not replacing the EGR, but I will not be adding any more aftermarket fuel cleaners, as I've heard from more than one person that nowadays they simply are unnecessary, as long as you avoid commodity gasoline (e.G, the kind sold at a large grocery store, like Safeway).
My rule is from my training at mechanics school: Rule #1: If it's not broke, don't fix it.
Sometimes, also the cavalier has a problem with the idle air control valve, a $40 part that is easy to replace so you might want to check that out. The OBD (on-board diagnostics) will give you the trouble code and I would go from there, since you want to repair the right system or part.
Thursday, March 21st, 2013 AT 11:36 PM