Ok, I have a 1991 Z28 Camaro with a 305 TPI and a T-5 transmission. It has the G92 package and 186k on the odometer.

So, the problem is when I'm driving car is normal everything seems fine. Then the car will buck and have feels like a mis-fire then my speedometer quits and the Service Engine Soon (SES) light comes on. The car still seems to run ok, but I can smell it running very rich. It will do the same thing again and the SES will go off and the speedo will work again. The car also idles high when the speedo goes out. Sometimes the car will die out when ideling.

I did a search and pulled up the codes. I have a code 12 (big suprise we can ignore that one) a code 33 which says "MAP Sensor Voltage Low- Pressure low/Vaccum High" and "MAF - Signal High - Flow Low (EFI/TPI/SFI)" I'm also pulling a code 51 which said "ECM, PROM, or Mem-Cal Failure.

Any help would really be appreciated. Thanks in advance guys.

 

The more significant error here is the "51." That is common when the PROM is not connected well to the MEMCAL, or the MEMCAL is loose on the ECM mainboard. Either way, you'll have to open the ECM and reseat the MEMCAL and PROM.

The "33" may clear up after this. If not, you may also want to check TPS voltage (even though your's is non-adjustable) and make certain the distributor connections are intact.

 

yea i got a code 51 and some other timing error code and after i replaced my chip it went away. of course i also replaced the ecm last year.

 

I dont really have the money to replace the PROM ATM and I dont want to because i'm still thinking of swapping in a 350. So if I do i'll need a new chip anyways. I hope maybe it does just need re-seated. I guess I can try that, but I've never had to mess with the computer before and not looking forward to it. Would this be a very difficult task?