my brother in law has a 93 prelude with a bad surging idle problem. I had him pull off the iacv and the screen was blocked with stuff so he claned that and the lines. still did it so i had him pull off the fitv and we saw the plunger was almost all the way out. so i screwed it back in- we started the car and it ran great for a few minutes no reving. but he shut it off and turned it on and back to the surging idle- it has plenty of coolant. but while its running, if you unplug the TPS wires off the sensor then the surge goes away but the idle raises kinda high, but steady. could this be a faulty TPS sensor?

 

I have a 93 H22 motor in my car and it sounds like you having the same problem as me. So if you ever figure out the problem let me know. And by the way where is the FITV located at on our motors?