for starters I got the car this way. Its a 91 camaro rs with a 89 ecu. We rebuilt the motor and it ran for about a week and then it died. the ecu is pooring way too much fuel in the motor causing not to run. check engine lights include water temp sensor, map sensor and bad ecu, all of which have been replaced but the codes still come up. the tach pegs out when it does run, but i assume thats not related. when the car does decide to run the idle stumbles like its missing, then all of the sudden it will run perfect, then like crap again. all within a min. or so. if you try to give it WOL. it stall immediately. the plugs are completly back and oilling from running to rich. ALso replaced the ignition coil. b/c we thought we weren't getting enough spark. im about clueless now. What really baffles me is the 89 ecu. the 91 ecu we first bought didn't fit the harness and thats when we discovered it had a 89 ecu. any help is appreciated.

 

The biggest red flag I got here is that the 1989 ran MAF and the 1991 ran Speed Density. The computers interpret information differently. With the MAF system, they use the ACTUAL measure of the airflow going through the MAF sensor to determine the fuel delivered whereas the SD system uses a prescribed mathematical formula to determine fuel delivered based on the pressure (and engine speed) in the manifold. I'd be willing to bet a king's ransom that if you put a correct ecm for the year/engine your problems would be solved. Possibly you had the 91 ecu for a 305 instead of a 350? Or vice versa? I'm a little less certain on that part of it, but I would think in no way is a 1989 system compatible with a 1991. A 1989 doesn't have a MAP sensor, that I do know. Good luck!