Hi, I am having problems with my 91 civic si. I will start by saying, I just recently completed a motor swap (installed a JDM d15b vtec). Due to money situations I have not been able to buy the proper ECU, conversion harness, and dizzy. Since the motor swap the car has been running rough, I believed it to be because the timing was off a bit, but it has gotten progressively worse. The main issue I am having with the car is it seems to be running very rich, and or loading really bad. Around 3-4k rpm in every gear the car will sputter, jerk, pop and smoke, and nearly die. How I seem to keep the car running it to change gears early and keep the car at very low rpms or very high rpms. The car is smoking very bad, I believe it is gasoline I am seeing. I am not really sure what to do, my car is dying and I need help!

 

Is the timing right? You have to have both cams in time as well as the sparks.

Check the fuel pressure with a gauge.

Remove spark plugs and inspect if they are all the same black or if the problem is only on some cylinders.