HELP me figure out wtf is wrong w/my car! Please?
OK, I've got a 2000 Z24 Cavalier. Let me rewind a little bit to start. The car broke down on me one day a couple months ago and the check engine light was flashing. Ended up having to replace the ignition coils and spark plug boots and spark plugs. It was all better. NOW the check engine light came BACK on and if you hold the gas pedal down, it hesitates and misses and sputters. If you don't give it gas and just keep it steady, it doesn't do it. But if you're in 4th or 5th gear, it does it more often, and I have to down shift. So we took it to have it checked. The diagnostics machine said that it was an O2 sensor, probably the one closest to the catalytic converter, and the check engine light was cleared. So we changed that out. Still didn't help. The check engine light came BACK on not too long thereafter. We thought that maybe it was the fuel filter. We changed that (and it needed changed anyways). That didn't help with the problem. We even put fuel injector cleaner in. That didn't help. So we took it BACK to put it on the diagnostics machine. It was throwing out three codes now. It said 1) crankshaft sensor 2) O2 sensor at manifold and 3) Same O2 sensor again. So, he cleared the check engine light again and we bought the crankshaft sensor cause we were told that the crankshaft sensor being bad could throw the O2 sensor off and make it show up, too. We changed the crankshaft sensor out today. STILL DIDN'T HELP. No one can get a upstream O2 sensor for 2 days and we'll get that, but I have a feeling that that won't help,. So, a downstream O2 sensor, a new fuel filter, fuel injector cleaner, a crankshaft sensor, and MUCHAGGRAVATIONN later, we're still in the same place that we started. Anyone have any suggestions? I'm ready to push the car over the hill. If this upstream O2 sensor doesn't fix the problem, I don't know what to do. We will have spent well over $200 by then for nothing. And the check engine light isn't back on even tho the problem is still obvious. All you need to do is put it in 4th gear and push the gas pedal down and it does it. ANY help would be appreciated! Thanks! -Crystal

have you tried cleaning out the mass air meter, or the pcv valve?

i dunno how to fix it but it sounds like what my car used to do before i had the motor rebuilt... it did for a lil while after i got my car back and then it just quit

crank sensor? Clean your MAF with spray brake cleaner? Someone (mod) may be able to help.

The brake cleaner I have is just spray ethyl alcohol, maybe there are different kinds. I have some electrical contact cleaner as well.

I've always used electrical cleaner to clean mine. I've also used acetone with good results.

If the other advice doesn't help and the upstream one isn't the fix then you might try the throttle position sensor as well.

Try grounding the o2 sensor wire. Unplug it and run some leads into the harness. That should put the computer into open loop mode, running off pre programmed data instead of live data. If that fixes the problem, then its your o2 sensor.

Who excatly told u to change the crank sensor because more than likely if the crank sensor is bad U won't get ne fire at all.... I agree on the TPS..... and i can't remember if u said u changed the Ignition control module or not but it could possibly be the problem.....

You said you changed the coil, plugs and wires and that fixed it the first time, right? Back in the day when I was first getting into cars I changed plug wires (car was fine at the time) and did not use any of the grease that you are supposed to use on the boots (helps them from frying against the plug and coil connectors). A few weeks later my car started missing, mainly when giving it a decent amount of gas when there was a load on the engine (up hill or something like that). Went to take the plug wires off and 2 of them would not come off the plugs. Had to end up breaking them to get them off. The rubber boot had basically melted against the plug and was causing a short. Put in new plugs, put the stock wires back on and all was right with the world. Check that since it's recently been changed, and be sure to use some of that grease if you hacen't already (I think it's called di-electric grease). Autozone and Advance both carry it if you need some. If that's not it then I got more questions. It's possible the car might have skipped a tooth on the timing belt, but usually that will make the idle and the whole RPM range feel bad. Jason

fuel pump is going bad. Where I work we have a fleet of 25 cavys. EVERYONE has lost a fuel pump at apx. 100k miles. Same symptoms as you are describing. Also, wasn't the cavy speed density setup? I thought they used a map sensor as opposed to a maf? I know the pre95's were SD and 02+ are. SQ