Are you just pluggin in the 88-89 box? There definitely is something to be done to use it with an 87 harness. Can't remember what I did. Got the info off of SQC and did it with no muss.

Like Eddy said, use the 87 knockbox for now if you still can and get it running.


Big Truck: 00, 3.5, Endeavor, 5-Spd drive line in hand!
Little Truck: 87, 2.6T I/C, MT, LSDs, Tonneau Top
Her Truck: 03, 3.8, 20th Anniv, 65k
Daughter's: 06 Eclipse, Keeping it Mitsu!
FSMs: MitsubishiLinks.com