After driving the car for about 20-30 minutes, the idle tends to fluctuate fron like 900, drops to like 4-500ish, and climbs back up and keeps doin that while the cars hot, any ideas on what it could be?

 

possibly the fast idle valve

 

IAC sensor may be bad or need cleaning

 

air in the cooling system...blead the system...the bleeder should be next/on thermostat housing..

 

fast idle thermo valve only works when the car is cold. IAC idle air control valve is the valve that would be working when the car is warm.

 

that is true, the iacv is the problem for many many people.
i wonder why that thing always breaks ,mabee there is a way to fix that thing?

 

Searching is your friend. This was recently a topic, and specifically the IAV...
https://honda-tech.com/zerothread?id=834768
There is a pic of what do. Good luck man!

 

if it was the iac it would either idle really high as in a vacuum leak or idle low...it wouldn't surge...trust me...bleed the sytem b4 you spend money...

 

on my ol' 89 that was the O2 sensor that did that... poor baby... may she rest in peace...

 

I recently pulled my engine to rebuild it and when i put it back in i had a surging idle only when the car was warm, or warm outside. I was stumped for a day or two and then realized that i hadn't capped off vacuum lines in two places. One on the intake mani that led to little black box that is incorporated into the stock air intake, and a line that went to the intake mani and down to the cruise control which i removed. Capped off the two lines and it purrs like a kittin during idle now!

 

What components are run off of the cooling system? FITV, IACV? New to Hondas I'm curious. Gonna bleed system tomorrow, then start inspecting and cleaning/replacing valves and sensors until it is fixed.