I tried the engine swap guys,and there where no coments made.I'm trying to find out if the engine wiring harness on an 1986 2.8 v6 is the same as a 1990 3.1 v6.I can find a 3.1 easyer than a 2.8 efi

 

Not even close. The C100 bulkhead connector needs to be rewired, the windshield wiper harness needs to be installed in the engine harness side of said C100, the gray 6-wire connector down by the ECM needs to be rewired and have some wires switched with the 15-wire connector next to it, the oil pressure sender, TPS, IAC need to be rewired, and you will need to find a way to get a VATS signal to the ECM so you have fuel delivery.

Shoot me your email addy, and I can send you the write-up I have on it...

:edit: What are you looking to do? You already have the better P4 system.

 

I found a 3.1 close to home.Just having a hard time finding a 2.8 fuel injected to go in my sons 86 bird.There is one I found 6 hours away.

 

Well, if that's the case, don't even think about touching the wiring harness. Remove the smog pump (keep the pipe in the exhaust manifold, however), upper plenum with throttle body, and the fuel rail from the 3.1. Keep the fuel injectors or don't, it's up to you, they're pretty much the same (actually, the fuel injectors used on the 88+ 2.8 were 3.1 fuel injectors). You will need to pop the plug out of the hole for the seventh cold start injector out of the back of the intake manifold (the lowest one), and put the CSI from the 2.8 in the hole. Put the nylon idle air pipe on the nipple at the back of the manifold, the hose on the PCV valve, and run the pipe to the front of the engine. Install the 2.8 fuel rail, upper plenum, and the throttle body, complete. Swap over the 2.8 alternator, oil filter adaptor (or you have to buy a connector for the single oil pressure unit), and air intake.

Install the "new" engine and crank it up. However, if the transmissions in the 2 cars are different, keep in mind that the 86 2.8 is externally balanced and the 3.1 is internally balanced. So, if you need a flywheel, you need one without a balance weight on it. Same for the flexplate... Get the plate or wheel matching the engine, not the car.