I have a 91 305 z28. Just wondering how you would run the factory gauges without the cpu. Are they on their own program or do they all go through the ecm? I know the temp sensor has one for the ecm and one for the dash, but do they both go through the ecm first.

 

There are two wires in the firewall connector that goes directly to the guages for temp and oil. I do not know about the speedo. Sorry I could no be any more help.

 

Im not going to be much more help, but, when I removed my ecm from my '86 Z28, all the gauges were on their own harness. BUT, the '86 has a cable speedo, and yours has a elec one im sure.

Good luck on your car!!

 

I was told that I had to leave the old computer in for the gauges to work. I didnt beleave them so i pulled it out. All my gauges still work just no idiot lights.

 

If it is TPI you should be able to install a VSS buffer to run the speedo and cruise. If it is TBI you should allready have the VSS buffer in the car. The rest of the gauges do not run through the computer.

 

long&low is right i unpugged the ecm in my 91 firebird that was tbi but now carb and it started up and everything was ok the only thing i didnt do was drive it to see if the speedo worked but it should ill post when i find out. with that in mind i think im going to take out all the ecm wiring since it seems to be a different harness. Ill reply when i find out.

 

VSS works independent of the ECM. The speedo will work as long as the wires related to the VSS weren't hacked.

 

The speedo worked in mine i see no reson why it wont work in yours.

 

I can verify this i tested it out today and working find besides being way off because of the 4.11 gears. One thing though you no longer get the fuel pump prime. But with the carb the bowls should be full so it should be allright.