Ok, so bear with me as this is just a theory of mine that I'm looking to get opinions on. So my 2000 accord, f23a4 motor, 5 speed manual, 141,xxx miles acts like it has a vacuum leak. I looked over all the vacuum lines and what not and found only one spot that had a crack, so i switched out that section of line and its better but not completely better. Now this is where it gets funny. If i unplug my IACV, the idle doesnt change to where it should for where my idle adjust screw is, instead it starts surging quickly from 1000-1200 rpms. Now, I know that surging is something that can be caused by vacuum leaks but like i said, i fixed the only leak i found. If i remember right, the IACV is supposed to close completely when it gets unplugged, so if my IACV is bad and it doesn't close completely when it gets unplugged, it could act like a vacuum leak because of the extra air getting through the valve that should be closed. any ideas?

 

iacv is no good...Try taking it off..use some brake cleaner and a tooth brush to clean the lil filter and put some WD-40 inside the lil piston and it should work just fine

 

No, if the iacv completely closed your car would die when you unplugged it. The idle bypasses the throttle plate by some way and that way is the iacv. When you unplug the iacv the ecu simply doesn't regulate it by opening it.

Given that the idle surges when you do unplug it that means there is a vacuum leak somewhere else. I only use carb cleaner when cleaning out anything intake related. The gaskets inside the iacv are very delicate and are just looking for reasons to go bad. Also, do NOT spray anything inside that thing when it is in any way warm as the gaskets inside will swell and come part when combined with an additive.

 

I kinda figure its something with the iacv, ive already cleaned it and all the problems are still there, plus, when i had it off before it little valve didnt close all the way cause when i sprayed one passage with carb cleaner, it leaked right past the valve and into the other passage. i'll try a $20 junk yard iacv and new gaskets from an auto parts store before i shell out the $300 to get a new one haha

 

Like I said, nothing you reported suggests it is bad. It sounds like the leak is elsewhere.