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I thought I had my Corsica running again after 8 months. Just turned over 94,000. It had a terrible Idle, and stalled everytime I touched the throttle. First I replaced plugs/wires, all three coils. Nothing. I read the OBD1 codes and got 33 and 35. IAC and MAP. I replaced the idle control valve next and still nothing. When I replaced the MAP sensor that is when I thought I had the thing solved. It ran perfect and drove around amazing like the problem was solved. But this morning when I started it up its doing the same exact thing again, but now only throwing a 33 code. I exchanged the MAF in case it was a faulty one but no luck. fuel pressure stays at 40 PSI while idling. All 6 Injectors were replaced in 2010 at 85,000 miles so im stumped.

BoxLiveFresh wrote:I thought I had my Corsica running again after 8 months. Just turned over 94,000. It had a terrible Idle, and stalled everytime I touched the throttle. First I replaced plugs/wires, all three coils. Nothing. I read the OBD1 codes and got 33 and 35. IAC and MAP. I replaced the idle control valve next and still nothing. When I replaced the MAP sensor that is when I thought I had the thing solved. It ran perfect and drove around amazing like the problem was solved. But this morning when I started it up its doing the same exact thing again, but now only throwing a 33 code. I exchanged the MAF in case it was a faulty one but no luck. fuel pressure stays at 40 PSI while idling. All 6 Injectors were replaced in 2010 at 85,000 miles so im stumped.

Symptoms certainly sound like a bad MAP sensor. Make sure the vacuum line is plugged in and isn't cracked or broken -at 30 years old, the vacuum line or tee could have given up when you replaced the sensor, and just waited for another heating cycle to break loose. 40 psi fuel pressure is a little high at idle vacuum, so a broken vacuum line to the regulator could cause both symptoms if the FPR vacuum line is teed off of the MAP sensor vacuum fitting.

If you have a volt/Ohm-meter, check reference voltage to ground (5V unplugged from the MAP sensor, Key on Engine off), double check ground line continuity at the sensor, and you can also run a continuity test on the signal wire from the MAP connector to the ECM under the dash... If you have a way of reading live data from the ALDL connector (GM or OBD-1 Scan-tool or data-cable and laptop with appropriate software), you can see what the ECM is actually reading for MAP, and can also use a vacuum pump to test live data from the MAP sensor in the ECM.

Good luck, keep us updated on the progress.

Ok so I left the car sitting for 24 Hours, and prepared to go at the thing with a voltmeter like you said rettax..
I decided I would fire it up real quick, and now It runs, and drives around (doesn't die when opening throttle) and no codes. After I returned from about a 10 minute drive, the car idles rough but stable enough. (see video) Were hitting it right now with the volt meter. Also I will check the vac lines now.

Hmm, my corsica started running like that exactly when i unplugged MAP-sensor. I got -93 model with 3.1, but base is same. I would check the wiring. Also did you already just pop the battery out and reset the ecu? You never know whats causing the craziness...

Btw: That interior looks so good... i hope i had earlier model corsica. Can we get more pics or videos?

Still working on this thing... So far I have replaced:

IAC
MAP
TPS
02 Sensor
Plugs
Wires
Coils

Also just recently dropped the tank and purged all the bad gas. Fuel pump filter sock looked good, the pump itself buzzes. The car is less stable at this point, stalling after less than a minute of erratic idling. Going to leave the battery unplugged overnight to hopefully reset the ECU. Tomorrow I will try changing the fuel filter, and cleaning the EGR. I will go over hoses and wires as well.

Definitely sounds like a vacuum line is broken somewhere.

Injectors? 2.8 is famous about them.

Bapsu wrote:Injectors? 2.8 is famous about them.

Shop diagnosis says it's injectors. Going to replace them this weekend or the next.