91-94 ECU In 90

[805eclipse]

So i bought a 90 gsx and i knew that the ecu wasnt original because it wasnt even bolted in, it was sitting on the passenger carpet plugged in and also had some stickers on it proving it was rebuilt. i assume it is not a 90 ecu because the tach doesnt work and i heard that is what will happen if you use a non 90 ecu. what im confused about is from what i have read in order to use a 91-94 ecu in a 1990 you have to swap out the coil pack and power transistor unit to match the ecu and swap some wires to make it work properly. i doubt that any of that was done as i have a 91-94 power transistor unit and it cannot connect the the harness, and my tach does not work. i get no check engine lights and the car runs really strong so what problems could i run into if the coil pack and ptu were not switched when the 91-94 ecu was put in? i cannot pass smog my co is 10% over at idle, could this be why?

 

[luv2rallye]

converting a 1990 to a 1991-1994 ecu system
http://www.dsmtuners.com/forums/problem-diagnosis/210441-ecus.html

 

[Nobrakes]

I am putting a 1992 ECU in my 1990 plymouth laser. I found this thread helped me out alot and for the person that is havig tack problems this tread will tell you how to fix it vers eazy.
http://www.dsmtuners.com/forums/art...4-ecu-swap-into-1990-dsm-ignition-wiring.html