Hey, I have a complete but wrecked 87 TII and wanted to put the entire drivetrain in a 90 GXL. Everything seemed pretty straightforward until I looked at the connectors on both ECUs. There are three plugs on each unit, and the plug that stays with the car is totally different. Will that ENTIRE harness have to come out of the 87 TII? Does the dash have to come out to get to that harness? Can someone tell me what that harness controls? I suppose most people that do the N/A to TII swap have the same series car....HELP PLEASE

 

The harness does have to come out. It only deals with the motor. Nothing on the left side of the car is involved. The harness plugs into the ecu, knock sensor box, and a few other things behind the glovebox. And then goes into the engine bay, where it plugs into the cruise control, some emission stuff, resister pack(for the injectors), then it goes over the motor were it connects to the water temp sensor, tps, crank angle sensor, coils, knock sensor, then it goes toward the back of the engine where is ends with the injectors. That’s all! (I missed a few thing, but you get the idea)

YOu will need to take the UIM to get to the injector plugs and a few others. Its not as hard as it seems. I had to make one from scratch and install it because mine had a short. So 200 feet off speaker wire and 8 hours later I had mine in. It will take about 1-2 hour to take the old one out and the same to put the new on in.

 

I already have the engine harness out. The harness with 2 separate yellow plugs that go to the ECU. But there is another harness that stays in the car and goes up under the center of the dash. This plug is shaped totally different on both cars and clearly prevents a simple ECU and harness swap with the engine. I think I have to swap that other harness by taking the dash out. But I was hoping someone had swapped an older engine and ECU into a newer (s5) car. Anyone else? I assume that harness provides power tothe ECU?