RE: 99 Cavalier Rough Idle issue -Update
 

The new wires didn't help. My cousin that works at a GM dealership brought over their OBD meter (lots of extra options on that one!).

When the car is idling at 830-850 rpm you can watch the mis-fires on cylinder 4 going up. Take it up to 1000 rpm and they stop and the engine smooths out just fine. All the sensors are working correctly.

So, I plan to take it up to his house in a week or two and we are going to pull the head. His guess is a burnt exhaust valve. He said he would do that before we put a used engine in it as otherwise mine is in great shape. If we pull it and its worse then we can go the used engine route.

RE: 99 Cavalier Rough Idle issue -Update
 

Any updates?

RE: 99 Cavalier Rough Idle issue -Update
 

Yes, We worked on it a week and a half ago. We couldn't get the compression to come up on cylinder 4 (one with mis-fire). We pulled the head (hoping it was a valve). Valves looked like 128,000 miles but were OK; it wasn't a valve issue.

This pointed to possibly compression rings etc; so I opted for a used engine (vs tearing this one down any further). We put an engine from a 2000 Cavalier that had 42,000 miles on it; car runs great now.

Cost including labor was $1,500 and since the rest of the car is in great shape it still beats buying a new car.

similar issue
 

I have recent trouble with my 97 cavalier. It starts rough and idles high until you gas it a bit. I had the plugs & wires replaced and started running some sea foam & mystery oil through it. Also, the fuel filter is not too old at all.
It's been a great car & I put 150,000 miles on it! I'd hate to dump alot of money into it if there is a simple fix??? I didn't want to mess with the idle adjustment, but not sure if it's safe to keep driving without doing something else for it.
I'm not getting any bad readings on my handheld computer and the engine light doesn't come on.
Any suggestions?

James

I just finished resolving this issue on my 95 Cavalier. It began misfiring and sputtering bad at idle and up to about 5mph then smoothed out as well. It went away for a day, then came back a few days later but even worse and sputtering occasionally throughout any speed or engine rpm it was at. It would break up so bad at around 45mph or so and I could not accelerate past about 50. It happened after I floored the pedal in an attempt to race a friend in their cavalier, but the car only sputtered and bogged down, moving nowhere. I found that the car was misfiring on cylinder 1 and was running rich because of it (determined this from the look of my spark plug in cyl 1, was dry fouled compared o the others which were fine). I replaced spark plugs and tried again, no difference. Replaced plug wires, no difference. I then replaced the COIL PACKS and went for a drive, car ran smooth and the problem was resolved. Took it on the highway up to 75, ran perfectly fine. For anyone wanting to attempt replacing their coil packs on the older cavaliers (95-97 maybe?), it is not fun. If your spark plug wires run behind the engine and under the intake manifold like mine did, you will have to remove your A/C compressor to gain hand access to the coil packs. Use a wide variety of extensions and a 7/32 socket to get the bolts off, it's tricky. DO NOT remove both coils at once, or you will have to blindly line up bolts and the plate the packs sit on to the bolt holes in the back of the block. Hope this helps, good luck