I have an 86 Iroc that has an 89 Firebird motor. When the motor was changed they also changed the harness, for what reason I do not know as I thought that they were all the same? The car runs and drives but the nothing is hooked up on the inside. The Firebird inside harness is completely different and its about to drive me insane. I have tried several manuals to help me sort it all out but to no avail. My question is can I just switch backt to the Camaro inside harness? Unscrew the plug at the firewall and just switch? I have the old harness all except of course the inside! So i will have to go get one but I can handle that if it will work. If I can't just change the inside harness is there any reason I can't put the Camaro harness on the firebird engine and then switch the inside harness? Any help would be of great benefit to me! I am about to give up.
THANKS

 

you should be able to use the original wiring harness. I believe there are actually 2 harnesses in these cars. There's the computer harness, for stuff like sensors, fuel injectors, solenoids, etc., and then there's the main harness for things like headlights, wipers, accessories, gauge senders, ignition, and so forth. If you follow the wire routing under the hood you will see all the computer stuff going toward the passenger side of the firewall, and all the other stuff going toward the driver's side of the firewall. The two harnessess to incerconnect in a few places inside the car, for a few things like vss signal(depending on model/year) and one or two other things I think. I would get your hands on a wiring diagram for your current car, and one for the donor car the engine came from, and study them for a while. That's really the only way you're going to figure out what can stay and what needs to go.