Can you help me or direct me to someone who can? I bought this 94 Z.Auto.Its been a nightmare.Someone had replaced everything with '93 motor,trans,wiring harness and comp.I replaced the wiring harness and trans to '94,and the comp is from a 95 TransAm.Its idling fast,backfiring through the carb.Ive checked all the connectors,replaced the EGR valve,etc.,etc.,Do you think the comp is incompatible?The only code im getting now is EGR circuit.

 

I believe the 93 engine has a different IAC connector than the 94 wiring harness. Have you checked that? (This assumes you are still running eectronic fuel injection - see quote below).

What really confuses me it this statement:

When they installed the 93 engine, did they convert it from EFI to a carburetor?

I think the 95 PCM is set to use pulse width modulation (PWM) for the tranny converter lockup, while the 94 trans is switched lockup.

 

I'd bet he's referring to the throttle body as a carb.

The 93 was vastly different than subsequent years. Different fuel system components. Smaller injectors that were batch fired and more.

The EGR circuit has nothing to do with the EGR valve. The PCM is monitoring the connection to the EGR solenoid. The lines that connect to the PCM that control things are also monitored to see if those items are still connected. Those lines, if bad, can either be open, shorted to ground or shorted to supply voltage.

If your going to continue to work on this Rube Goldberg, I suggest you get a hold of a 93 shop manual and a 94 shop manual.