when I cold start the car in the morning, the idle surges from 1100 to about 1500. Kinda like when you have a vacuum line leak or air bubbles in the coolant. But the weird thing is that it just does it a couple of times and then goes back to normal and is completely normal after that.

I've checked all the vacuum hoses and can't figure out what can be causing this.

 

Hey Vlude, mine does the same thing and all my hoses, etc seems to be normal too. I have no clue to what causes this. Anyone else with answers?

 

Could be your IACV or you need an oil change... There is DIY's to clean out the IACV just googlize it...

 

i dont think an oil change has anything to do with a surging idle...correct me if i'm wrong...a coolant flush or low coolant will however effect the idle...to the OP: read this thread frome the FAQ it should help

https://honda-tech.com/forums/honda-prelude-4/end-all-idle-surge-bounce-etc-problems-thread-1979500/

 

My lude does this as well, and I know it doesn't need an oil change and there are no leaks. It does it only when it's cold, as if it's trying to warm itself up...

 

ok, I have not fixed it yet but I think I might know what caused it. I cleaned out my IACV valve a month ago and of course the coolant leaked out from it. I think that it got some air bubbles in the coolant lines because of that.

I will bleed my coolant this weekend and report back. Hopefully, this was the cause. What is weird though is that this only started happening about a month after the IACV cleaning.

 

FITV.. located under the throttlebody. i'll bet my left ******** that solves your problems guys.

 

im with dagle on this one...take off the fitv and adjust that white plastic nut down. that should fix it.

 

Mine does that too when it's cold out...Hmmmm...Guess i'm gonna make her bleed! PUN INTENDED...