Hey was up.. Okay my friend got a 90 CRX si... he has in it a SOHC ZC... it was running fine but was in a accident so was off the road for a few months... we just fixed the frame and it started right up with a jump no problems. We decided to try and put a b16a1 ecu on the car to see how it would run and it ran great. but then came the problems. it does a lot of crazy things like for instance it will run and idle normal but if you turn on the headlights the engine starts puttering... why? also if you are driving the hot cold meter is normal but when u hit the brake the needle goes all the way up to hot... while he is driving the rpm will start to jump around too.... whats wrong????? we put a reg si ecu on and it still has problems... help me please!!!!!!!!!!!!

 

Sounds like a ground problem.

 

well we just replaced the battery and alternator on it with brand new ones... i checked all the grounds and everything was on straight.. unless there is one i dont know about or something? wha else can it be?

 

where are all the grounds?

 

Why is a B16A ecu running an SOHC ZC?

 

because we were seeing how it would run.... but that aint the problem cuz we put the si ecu back in and it is still the same.... any suggestions? and where are all the grounds?

 

on these older cars jumps can be very bad...i'd troubleshoot the easy first...replace all the grounds if they are still original as you should do it anyway as it makes the car run smoother and stronger...if that works then great but i'd be worried that you might have shorted the wiring harness either on the engine or the main wiring that goes to the ecu or main relay on the car

do you have a helms manual for your crx? if not then it is a absolute need for the diy mechanic...it will show the grounds...if you don't have it then get a small flashlight and look for the wires...it is not hard to see them...i think the hardest one to find is on the engine wiring harness near the thermostat as it is well hidden

 

Could be that the ELD (in the underhood fuse panel) is toast. I agree that you should carefully check the grounds-but more important may be the ECU plugs. It really takes very little to cause damage or have some part that was corroded after 15 years cause the circuit to have more resistance than it should. I do have the Helm, but the drawings for an '89 may be off a little compared to your 90.
E-mail me if you need more help.