i have a 1990 civic dx 1.5 and with a blown engine, and my friend just gave me a 1994 civic 1.6 engine, im gonna drop it in the car some time in the future, only prob is i dont have the wire harness for the 1.6 engine, can i modify mine to fit the 1.6 engine and obd1 cpu, or do i have to find the harness for the 1.6.

 

You need to reuse your stock engine harness.
Then you need to convert from Dual Point Fuel Injection(two fuel injectors) to Mulit Point Fuel Injection(4 fuel injectors).
Here's info:http://www.fourthgenhatch.net/mpfi.html

Then you need to a obd0-obd1 jumper harness and a 4 wire o2 sensor.

 

just swap over the intake manifold and exhaust manifold for the time being and or use an Si harness. Or you can just use the DX harness and add all the correct wiring just search for DPFI to MPFI.