so I've been having idle problems with my civic, I start it up and it idles at 3k for a lil then drops to 1.5k and surges from 1.5k to 2.5k rpms, I replaced the iacv, cleaned fhe throttle body, replaced fhe map sensor, bled the coolant, flushed coolant and put in oem blue honda coolant, no cel when all connectors plugged in, i put my finger over the hole for the iacv in the throttle body while it was running and the idle drops and smooths out to about 1.3k rpms, so I unplug the iacv and it stays at 1.3k and then I mess with the idle screw and if you bottom it out the idle will go to down to about 1.1k but idles kinda funny still, I checked for vacuum leaks and there are none, im at a loss..

 

My h2b had the same problem and I tried everything like you did. Ended up just putting an iacv block off plate since my only component running off the engines power is my alternator so I figured I didn’t really need it. Fixed the problem. If you still have a/c, power steering, etc. you most likely need a new iacv. You can tell if its an iacv problem if it stops surging after you key off and on really quick to reset the cars electronics.