The other day I switched the computer in my 85 trans am with the comp. out of an 86. When i cranked the car the fan imediatly came on and you could here the intake sucking from inside the car. When I pulled out a drove down the road it ran great, but after about five minutes it started flooding the motor and backfired through the intake so I switched them back. So I was wondering if anyone else had done this and if it worked for ya'll. Any response would be great.
thanks

 

You have to change a few things for it to work right.
I can't remember everything off-hand of what you need to change, but the MAF burnoff setup needs to be changed.
go to www.thirdgen.org and post in the TPI forum there, they will let you know exactly what needs to be done to run the 165 ECM.

 

did you mess with your timing?

 

I haven't messed with the timing

 

ttt

 

check and make sure all your vaccum lines are connected

 

you changed/modified the harness, right? The way you said you put the old one back in, it sounds to me like you just unplugged one and plugged in the other. If that's what you did, I'm shocked that the car even ran.

To use an 86 computer in an 85, you either have to make a bunch of changes to the harness, or just do like I did and get a newer harness. The 86 harness is by far the easiest to swap in because it'll match up to your distributer & cooling fan. Everything is a 100% plug & play deal when using an 86 harness. The only difference is that you'll have an extra relay near the brake booster, but the relay is $10 and the bracket should already be drilled for the mounting screw.

The only other thing you have to do in order to use an 86 harness is to make the hole in the firewall a little bit bigger. Because the 86 harness has a couple more wires, the bulk-head is about 1/4" wider than the 85 piece.