I have 1991 Camaro Z28 5.7L with stage 2 performance chip, headers, new engine, etc. It has been running perfect since I purchased the car new in 91. But a couple of days ago while driving the car all of a sudden it started to run very rough and almost no acceleration. It acted similar to when you disconnect the ecm bybass connector, but it is not that, that makes it run worse. There is no check engine light. After shorting the A and B pins to get the computer codes it flashes the initial "12" code for handshaking then continues the 12. If there is no problem should the flashing indicator stop after 3 repititions, or does it continue? If not, does this mean that my speed signal sensor "code 12" on the tranny is bad?? Also after letting the car sit for a while, possibly cooling down as well, it goes right back to working fine again until another 5 min. of driving or so. Please give me some advise as to what to try next.
Thanks in advance!

 

Hi,

I have a 1991 camaro Z28 also.

I had a simuliar problem with the car losing power.

The culprit was the fuel pump....you may want to check yours.

 

Yes my 91 RS had that problem. The rubber hose that goes from the fuel pump to the rest of the in tank assembly was deterioriated. It was blowing most of the fuel right back into the tank. Went ahead and replaced the pump anyway. Also check the egr, maybe?