i have a 98 prelude and i read on a couple of forms were they plug up the upper hole in the TB and test to see if the idle stop surging.......Well when i do it, it just stalls out the car...haha i quess you can say it stop surging but the car is off. Thats what i dont get. also i tried to unplug the 2 pin connector on the IACV and the car stayed on. When i pluged it back up it idled higher. Is that a bad IACV? and can it cause my car to surge when idleing at the light? ive checked for vacum leaks cleaned the IACV, and tighten down the FITV...and sprayed throttle cleaner all around the vac hoses and intake manifold. i dont know im stump'd!

 

hmm sounds like a tough one. i think you may have to take it to a mechanic.

 

i thoguht you guys were mechanic's? haha just kidding im trying to see if i can fix it my self i no it has to be something simple. maybe something is clogged i dont know should i just get a tune up and see what will happen?

 

Is the idle surge happening only when the car is cold, only when it's warm, or all the time? How bad is it (what rpm ranges)?

Your idle speed should lower when you unplug the IACV, but not completely die. I believe your idle should be about 500rpm w/o IACV and around 750 with it plugged in when no accessories are on.

 

It happens after 10 mins or drivin or so and when I unplug the iacv the idle stays normal my cel light comes on n when I plug it back in the idle goes from 750 to 1000. Sometimes the idle jumps 750 to 1500. After driving for a while it idles at 1400 or so and stays there I think its the iacv but I just want to make sure

 

yeah this SAME EXACT thread is here.
https://honda-tech.com/zerothread/2421019

im haveing the same problem.. when i unplug that iac it idles at about 500.
i have a band new IAC i just got yesterday and next weekend its getting swaped out...

im gonna make sure theres not any air pockets in the coolent lines (the link in my thread some one gave me) says that thats a very good possiability... and when my motor got swaped it prob. did get some air in the lines b.c lines say in the car and so dose the radiatior and i personaly didnt do the swap so who knows if the coolent was propperly toped off... do some research... and ill be able to give u a result by the end of next weekend


oh yeah.. its the bottem hole in the TB not the top 2

 

if im not mistaken if ur idle stays at 1400 u have a vacuum leak

The idle adjustment screw fell out of my TB once and the idle wouldn't get below 1800rpm....ever, until i put a new one in

 

My $.02 - The CAV wax valve is loose/leaking. To fix the problem, the idle screw has been adjusted to lower the idle. So, when you block the air hole, idle is too low. Start by increasing idle adjustment - then cover the cold air valve hole.

There is another thread somewhere on this - basically, there is a screw in the bottom of the wax temperature valve that comes loose. Vibration causes intermittent leak and surging. The screw should be snug, but not Navy ship tight. - I would be this fixes the problem.