Will start and run good for about 10 sec. then runs rough, like a miss. Soon as you step on gas engine dies. Have replaced computer, ignition module, coil packs, crank sensor, map sensor, maf sensor, knock sensor, idle air control valve, tps and egr valve. No vacuum leaks, removed air plenum and checked vacuum lines, injectors and fuel psi. Has new fuel pump. HELP! don't know what it could be. About ready for big hammer.:confused:

Check the harness between the crank sensor and the ICM. It runs near the axle shaft, the balancer and near the exhaust manifolds, so it could be melted or rubbed through. Also have the ICM checked, as it could be a bad new part (especially if you bought a cheap brand one like Zenith or Wells).

have checked the harness, it is okay, no rubbing or burn spots. when engine is idling, can squirt carb cleaner into throttle body and engine will rev up, fuel filter is clear. checked bolts on throttle body and checked air filter. fuel psi at 40.:uhoh:

Has your cat. converter ever been changed ? You should also perform a compression test to rule out a cracked head or head gasket.

have checed the cat, same with or without. will have to check compression, once in a while the car would run fine, next a.m., won't ?:screwy:

You don't think you got bad gas do you ?

First, check fuel pressure at prime, engine off, ignition switch on. Next, check after you turn swith off/on two times, with a 5 sec pause in between. Now, start the engine and check idle pressure. Finally, (if it will), accelerate rapidly and check the pressure drop. Post back with your findings.

gas is good,fresh. will do psi checks in the morn. thanks!

sorry i have'nt replied. took car into shop for repairs. appreciate all the help and comments. thanks!:iceslolan

Finally got car back from garage.Could'nt fix it so they gave up. What happened was the previous owner had replaced the computer, then trew away old one. Did not change prom. The car has run good a couple times then goes back to crap. Now, if I disconnect the alternator, can rev car up but still not running smooth. As soon as I plug the alternator in, it instantly runs bad, cannot rev engine or it wiil quit. Alternator is good, have used different alternator and computer, no change.Not sure what to do now. About ready to take it to junk yard. Any more suggestions?:screwy:

I've got an '89 Regal with the same problem. Pulled codes and got 33 & 34. MAP & MAF. I don't have a MAF so I disconnected the wires to the MAP. When I dixconnected the vacuume line I accidently broke it off. I found at the other end, the fuel pressure regulator was part of the T. So I hooked the regulator direct to the source. It ran beautiful but high idle. I let it run for a while, then shut it down. Now it runs like crap again. HELP??!!

Good luck, Never did figure it out. Replaced the sensors, computer, coil packs, etc. Put too much into it, finally took it to the junk yard. Dead horse!

Replaced the sensors, computer, coil packs, etc. Put too much into it, finally took it to the junk yard. Dead horse!
Did you remove the new parts before taking it to the JY? If so, folks on eBay would be happy to buy them! :grinyes: