Urgent Z24 Help Needed!!

I have a 1988 Cavalier Z24 (2.8MPFI with 5speed trans) that is having some problems that I can't seem to solve. When I step hard on the gas pedal, the car bogs down and it starts to die out. If I step lightly on the gas (and i mean very lightly) it will rev ok. Car starts and idles ok. This problem can occur in neutral and in all 5 gears. This problem is wierd because it doesn't always happen, but I am absolutly certain that it is not a tranny or clutch problem. This occurs infrequently and sometimes the car will run like a champ for days. Sometimes if i'm already going 55mph and it starts to bog, I can downshift to a lower gear and it will eventually clear out and run ok. Check engine light does not come on at all. Diagnostic tests reveal nothing. On my own instinct, i did a full tune up, replaced the catalytic convertern and muffler, replaced the oxygen sensor, replaced the map sensor, and installed a new fuel pump and gas lines. I also checked the function on the TPS and it's input and output on voltage check out ok (it would throw on the check eng light if it wasn't working ok). The EGR valve is also functioning properly Car still bogs during heavy acceleration. Anyone ever had a similar problem? I am desparate to get this car running good again. I'm very attached to it and I'm very frustrated that I can't figure this out. I'm not a certified mechanic, but I do know a lot about car repair and this problem just escapes me. If you can provide any advice at all, it would be greatly appreciated. Thanks a lot guys.

I had that problem for about a month. In my case, I had just bought the car, and the fuel tank was full of trash. I dropped and drained the tank, put in a new fuel filter, and had all of the fuel injectors cleaned(had to replace 2 of them). That cleared my problem right up. It sounds like you've looked into the fuel system already though.
Good luck, and keep us posted!!:cool:

Honestly, i would check something simple like your oxygen sensor. I know it seems wierd, but it might be it, that's what my cousin's problem was in his Tahoe, and he had the same general problem as you.

Dude, i already replaced the oxygen sensor... said it above

I had a 90 Camaro RS that had that problem, but it was a transmission bracket/mount.

Im a certified ASE and GM technician and i would try a pcm.If you have a scan tool look for any codes that relate to the ignition control module.Also go try this go to your local GM dealer and get 2 cans of "top engine cleaner",its a cleaner than goes in the cylinders.Remove the plugs and put about 6oz in each cylinder and let it sit over night with the plugs out of it,next mornng spin it over and let it pump out all of the cleaner.Make sure to shut the hood when you do this,cleaner will make the paint really dull if it gets on it.After it has pumped out all the cleaner put the plugs back in it and go down the road and accelerate hard,it should smoke for a little while.What this cleaner does is remove all the carbon from the cylinders.Make sure to clean all under hood areas that the cleaner gets on.

Originally posted by 91Z24AUDIO
Im a certified ASE and GM technician and i would try a pcm.If you have a scan tool look for any codes that relate to the ignition control module.Also go try this go to your local GM dealer and get 2 cans of "top engine cleaner",its a cleaner than goes in the cylinders.Remove the plugs and put about 6oz in each cylinder and let it sit over night with the plugs out of it,next mornng spin it over and let it pump out all of the cleaner.Make sure to shut the hood when you do this,cleaner will make the paint really dull if it gets on it.After it has pumped out all the cleaner put the plugs back in it and go down the road and accelerate hard,it should smoke for a little while.What this cleaner does is remove all the carbon from the cylinders.Make sure to clean all under hood areas that the cleaner gets on.

Top engine cleaner gm pn#1050002 (use with caution!)

Try the top engine cleaner but your problem sounds like it may be in the primary ignition area, coil, module, crank sens, cam sens.

Also had tons of problems with intake leaks on those cars.

If I can remember correctly 88 was plagued with M.A.F. problems,E.c.m. problems 1227730 I believe and a series of prom updates.

I wanted to thank everyone for all of their input on the problem that I was having. In frustration, I was about to take the car to an authorized GM facility, but I read your comments and tried one more thing. I bought a new ECM (computer) and installed it. It was suprisingly cheap. It didn't cure the problem, but what it did do was throw the check enging light on. This means that the old ECM wasn't working properly because I never had this light come on. The good part is that after hooking up a diagnostic tool to read the code for the check engine light, we were able to pinpoint the problem. FUEL PRESSURE REGULATOR. It's located on the fuel rail under the air intake plenum. It's kind of a bitch to change, and the part costs about $100, but I will be very very happy to have my old Z running like a champ again. Thanks guys.

Glad to see you got it fixed:flash: