I have an 88 Convertable Z24. I bought it a couple months ago and it ran real crappy. Its been sitting 250 miles from home till I got time to get it. It started and ran very poorly.Tach showed 3000 rpm even though it was only running at idle speed. New fuel pump has 45 to 50 PSI. New fuel pump relay it had a rattle inside even though it worked I replaced. The Check engine light was on only code was for low fuel voltage. had no spark on # 2 & # 5 cylinders. put new coil on didn't fix tested coil it checked good. I replaced the ICM it now has spark on all 6 cylinders. starts and dies as soon as it gets to idle speed. tack reads 4000 when it dies even thought its only reaching about 900 or so before it quits. I have a new CPS and oil pressure sender on order should be here a couple days. wheile I hope thet will fix I'm not holding my breath. Any one have any Ideas?
I did not mess with the injectors since it ran before . I need to finixh the annual on my airplane it'll be next week befor I can get to them.
If you still get the faulty RPM readings after replacing the OPSU and CPS, then replace your ECM (Computer) or EPROM (chip in the ECM). You can buy a new ECM they don't come with the chip. Or you can use a used ECM, it doesn't matter what car or engine the ECM comes from as long as it's the right part number, but you MUST use your original EPROM or a matching EPROM in the new ECM!
Vehicles with the same part # for the ECM:
BUICK CENTURY (1987 - 1989)
BUICK SKYHAWK 1987
CADILLAC CIMARRON (1987 - 1988)
CHEVROLET BERETTA (1987 - 1993)
CHEVROLET CAMARO (1990 - 1992)
CHEVROLET CAVALIER (1987 - 1993)
CHEVROLET CELEBRITY (1987 - 1990)
CHEVROLET CORSICA (1987 - 1993)
OLDSMOBILE CUTLASS CIERA (1987 - 1989)
OLDSMOBILE CUTLASS CRUISER (1987 - 1989)
OLDSMOBILE FIRENZA 1987
PONTIAC 6000 (1987 - 1990)
PONTIAC FIREBIRD (1990 - 1992)
PONTIAC SUNBIRD (1990 - 1993)
CPS hasn't arrived yet. I pulled a ECM from a junkyard 88 Z24 it does the same thing. so I sent it i to have it tested. the one that was in the car is a junkyard 89 berretta at least that what is wrote on it. Next week I'll make a trip to town and get a set of noids so I can check the injectors.
got noids and all 6 connections flash. Did a Ohm check on injectors and 2 are way out from the other 4. so I ordered 6 injectors today. when they get here I'll change and let you know if it works.
try your crankcase sensor, i had a similar issue with my 89. what was happening was when the engine was cold the crankcase sensor was reading continuity. then after about 5 minutes or so( long enough for the motor to get hot) the cranksenser became open line and naturally the motor stalled. this made it really annoying to find but once i finally found the problem i changed the crank case sensor, along with the ICM and the problem went away runs great now.
Put all new injectors in and new crank position sensor. started and ran has no power idles rough. I got the ECM from another 88Z24 and changed it. the one install in the car has junkyard markings for 89 bretta on it. I took the exhaust off and the cat honey comb fell out in lots of pieces. It no longer sounds like its choking. put new stock exhaust for cat back on. starts and runs but has no power. did a compression check on the front cylinders they are all at 125psi cranking. I cant get to the back ones without taking the alternator off. checked the vacume its only 10 IN and steady at idle. pulled all the vacume lines I could find and plugged them. I also put a blockoff plate in the EGR no change. When its running I can pull the plug wires off two of the front cylinders and no change in the way it runs. pull the other wire off and it dies.All plugs and iwres are new. and when a tester is installed inline it lights up on all 6 plugs. so I bought all new coils today and hope to get them installed tonight.
Did you scan the ecm checking all the sensor? I had the same kind of prob. It would idle high and no power. It was the a open wire at the temp sensor by the thermostat housing for the ecm. If you have the same prop. after you replace the coils.
Finally running good. Re checked the compression 165 psi on all cylinders. Changed the timing chain it was loose but not that bad. rechecked the firing order twice. Pulled the upper intake again checked the new fuel injectors they ohm good. still ran like crap. Checked all the wiring again and checked all the vacuum lines. when running it sounds like a johndeere two cylinder tractor. when running pulling either the # 2 or # 6 plug wires make no difference but #4 will cause it to die. Pulled the intake and injectors again. swapped #2 and #4 injectors. then I put one of the old ones that ohm's good in the #2 position. I fired it up and it runs on six now. took for a short drive after it warmed up I could feel the timing set and it runs fairly good now. Next I need to put a new muffler on it I blew the old one up when it was backfiring. Only took four months to get it running. I'm now impressed with the performance its only a little better than my 4 cyl cav.I'm sure a 5 speed would make a difference. the auto just doesn't have a good ratio spread.
Nothing like trying to get so many items straightened out and finally get it back to normal or close enough.Glad it is better and may your other improvements and get a high flow muffler that might help with some mild air flow.Nice to here it finally paid off.