hello, i have just finished my b20vtec swap in my 1997 gsr. the car starts and idles great until i touch the gas then let off the gas. when i let off the gas the rpms will drop very low and die. when the motor dies i can hear the iacv making a humming/buzzing noise. i know that it is the iacv because the noise goes away when i unplug it.
here is a list of things that i have done to try and fix this.
-clean the iacv
-swapped the iacv with three different valves
-swapped the ecu (currently running a OBD1 P72)
-measured the voltage of the iacv plug
-i have tried to set the rpm with the screw on the throttle body(when the iacv is unplugged the car will die)
-checked the tps
-changed map sensors


so any and all help will be appreciated very much
thanks a lot bill

 

I had the same problem in my b20 (non vtec yet but soon) I noticed that humming too and then idle dropping. So what I did is also unplug the IACV then it goes away. But did you ever try taking out your intake piping with the IACV plugged in that humming will go away meaning to say that humming is your intake or air filter. As for the idle dropping. I ran an obd1 ecu and it ran fine without the idle dropping till this day, well not until i ran into problems again about RPM not passing 2K. Good luck.