So this is my first third gen. I picked it up to do a motor swap in as a roller. It was reportedly a former drag car as the heater a/c system had been deleted and blocked off. The pcm wiring was also chopped off in the engine bay. As the former owner was running a stand alone system. Turns out he was also a hack. the pcm is missing and so is the rest of the wiring for it. I can get it if I need it but I am transplanting a 5.3 auto into it. So I have to run the new pcm for the engine combo. But , my car has the digital dash in it. Where do the instruments get their signal from? from the engine sensors? or the pcm? what about the speedometer? I have the dash out and I don't see any cable drives anywhere.
I could use some help on this folks. I have to replace the floor pans and fix a bunch of rust but the worst is all the electrical. I have a bunch of parts coming for it. and am spending way too much to fix it but its the only way to get my moneys worth out of the car.
Another issue is on the brake pedal bracket there is a switch with vacuum hose on it. with the hose is also 4 or 5 wires. It runs about a foot and has been chopped off. where does it go?

 

Good news! Digital dash is not reliant on original PCM or harness. The only item you need to sort through is the speedo feed, but you can get it from the transplant wiring, no cable. Not sure exactly how, but you will find it through a search.

 

You need to get one of these Manuals for that Cluster,there is 14 pages just on that Digital Cluster alone,way to many to post here.
http://www.ebay.com/itm/1986-PONTIAC-FIREBIRD-SERVICE-SHOP-REPAIR-MANUAL-/141602315364?hash=item20f827dc64&vxp=mtr

 

Sad the things ya find when it comes to wiring , eh ? Kinda makes ya wonder how these people don't end up frying every wire in the car with their foolishness .

Anyway , Welcome to TGO , and I can tell you for certain that the vacuum line you mention is for the cruise control , it would dump the servo's vacuum the instant you step on the brake , thereby disengaging the pull the servo was putting on the throttle . The wires , at least two of them , are for the cruise control also , the other two likely having been from the converter lockup disengage (or maybe the brake lights ? I can't quite remember which functions were on which switch but it'll be one of the two)

I wish you well with the restoration .

 

Well that's the best news I have had since I brought this bucket home! I just found a bunch more rust on the cowl wheel well, floor pan, junction. I am already replacing floor pans due to rust. So thanks for the well wishes.....I have a feeling Im going to need them! lol