iacv issue..help please

I have a 91 integra. I did some searching and can’t seem to find out the answer. basically. with the iacv plugged in my car warms up idles up and down between 1000-2000 rpms. once I unplug it it ildes fine at 1000 rpms. and my check engine light comes on but I did a code check and nothing comes up. any ideas?

so what was the trouble code?

warmup should be at 1500RPM initiall then taper down to 1k, then finally stop at 750RPM when the car is fully warmed.

if you have bouncy idle, clean the IACV, check TPS, etc…

Most importantly get that code. you are reading it from the blinking LED on the passnger side I assume?

The fluctuating idle is not good. I believe the CEL should come on when you unplug the IACV. That is what happened when I unplugged mine, then when I plugged it back up, it went away.