i just did a b16a (obd1) swap in a 97 civic cx (obd2a), used b16 ecu and boomslang conversion harness (obd2a-obd1) with cx engine harness, pinned vtec, the car will not idle unless warmed up with IAC unpluged. changed IACV with known good one. idling problems continues. moved pins on ecu from a14-a12. checked injector wiring. checked timing multiple times and its perfect.

 

I put a DX mannifold on my CX motor and it was doing the same rought idle problem, so i changed the TPS, Map sensor and cleaned the IACV and it works perfectly now...not sure if it will work but its worth a try

 

check your cold start valve....that might be the problem...it was when i had my gsr swapped ek