First of I would like to say this has been a huge PITA. To make a long story short Im putting a 91-94 wiring harness in my 90. The parts I took from the 91-94 are the coil pack, ignitor, cas, tb, tps, fuel rail, and engine to ecu harness. Every thing under the hood plugged up fine. The problem is where it hooks to inside the car. There are 5 plugs on the harness inside the car. the three yellow plugs go to the ecu, one white plug goes to a fuel relay, the other white plug goes to the dash harness. My 1990 has 7 wires on the white plug(to dash harness), the plug on the 91-94 has 9 wires and the plug is different. I dont know what to do about this plug and why the 91-94 has 2 extra wires. If anyone has succesfully put a 91-94 harness in a 90 or knows anyone that has, please chime in. Im starting to think this is impossible.

http://www.dsmtuners.com/forums/showthread.php?t=181512
This is the only thing I could find about this connection. The two plugs are completely different and I cant splice the old plug to the new harness because there would be 2 extra wires.

Don't worry about the extra wires sticking out of the new 91 harness. There are about 4 wires coming out of it that are extra. the 91-94 chassis has a extra plug I believe for ABS.
I am not sure about this. I left those wires alone and my car run's perfect.

Thanks for the response. So I cut my 90 plug and splice it in to the 91 harness and just tape those 2 green wires out of the way?

I know I'm not exactly helping your particular problem, but... Is there something wrong w/ the harness you have in your 1990?

I had an electrical fire in the corner of my engine bay where the positive battery terminal grounded out. I probably could have repaired the harness but it would have been a ugly sight.

Thanks honduraneclipse!! These two green wires can be left alone. They just tap off of the tps wire and the air flow sensor. Pins 14 and 19 on the ecu. Hope this helps anyone trying to do this harness swap.

nc90awd said:

I had an electrical fire in the corner of my engine bay where the positive battery terminal grounded out. I probably could have repaired the harness but it would have been a ugly sight.

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WOW! at least more damage wasn't done!

Ok then you know about the easy pin swap for the 90 ecu into an 1991 car . Just trying to help w/out questioning your intelligence.

dsm-onster said:

WOW! at least more damage wasn't done!

Ok then you know about the easy pin swap for the 90 ecu into an 1991 car

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Im actually gonna use a 93 eprom ecu that I have. It turns out there is some bugs I need to work out, the "seatbelt/headlightpopup motor" fuse keeps blowing and I cant fuigure out why. Also the car wont turn over. I started the engine by putting 12v on the trigger wire and it started, but when I turn the key the relay under the radio just clicks.
Ive been working on this thing all day. Im to the point where Im just about to put a push-button starter on this thing