hamslice

Hey guys I just got a 92 Prelude with a H22a swap with around 10,000miles. The guy I bought it from said that there was a idle problem caused from a bad Idle Air Control Valve(IAC). Now when the car is cold it idles fine, until it is fully warmed up, then it jumps from 1500 rpm to about 800 rpm. Like, bwaaaa, bwaaa, bwaaaa...you get the picture. It never stalls out at idle just has a sporadic idle problem.
He said that this is common on H22's, so my question is do you think it really is the IAC Valve? He said he tried multiple other things and also swapped out the IAC Valve with his other H22's IAC Valve and said it idled fine after that. He just never got around to replacing it before I bought it. Thanks for any input!!!

G_Loc

If he replaced it with another IAC valve and it fixed it, then thats most likely the problem. A bad TPS can also cause a funny idle.

You can try taking the IACV off and cleaning it, that might help.

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petern101

my h22a swap did that if i didn't have a vacuum hose plugged in correctly

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hamslice

I'm pretty sure all the vacuum hoses are plugged in right. I really think it is the IAC, but I will probably try cleaning it first and then replace it.

hamslice

I forgot to say that when you unplug the IAC it idles fine but runs like **** when you start driving. But if plugged in it surges at idle and runs great.

G_Loc

I had that problem when my TPS was bad. IAC plugged in, idle was all over the place, but the car would hesitate alot and backfire... Check the TPS voltage.

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rayslude

there's a write-up here on resetting your IAC. Something to the effect of unplugging it, turning the throttle body screw to make your car idle at 800rpm then plugging the IAC back in. You also may have air in your coolant lines. Look up the write-up on how to properly bleed the system.

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hamslice

Alright, will do!

phialude

**** mines broke like 4 of those after i went boost, just change over to the S2K ones do u wont have to deal with that bs.

hamslice

**UPDATE** I recently purchased a new IAC Valve off Ebay for only $61 shipped!!! It is a genuine Honda OEM part too. I was going to tackle this myself. When swapping the Valves I need to disconnect two lines off the bottom of the valve. Are those vacuum hoses or coolant lines?
If coolant lines would I need to bleed the system before start up after installing the new valve in case there is any air in the line?

Please please...any response would help!!!! Thanks guys

rayslude

coolant lines, and yes, bleed/refill your coolant afterwards.

Look up the latest "bouncing idle" thread to give you a better idea of what you should do.

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Maharajamd

You have to set the idle lower then what you want it, and then the iacv will compensate the difference. after you are done cleaning/reinstalling the iacv, you will need to bleed your coolant lines again.

hamslice

Thanks guys I'll let you know how it goes.

TruNinja619

if you have a couple of vise grips.. just crimp both the coolant lines that go to the IACV... save your time going through the bleeding process...

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Maharajamd

Yea but all that is gonna do is keep it from leaking a little bit. When the coolant space is empty when u hook up the lines again, there will be an air pocket... So its pretty much pointless to do that...

hamslice

Yes...I too thought about how easy it would be to just pinch the lines. But then the thought came of the air pocket that would be there so I will just do it right the first time. Probably gonna tackle this tomorrow.

Maharajamd

Pretty easy. 2 12mm bolts, use a open box wrench. Clean the screen. Check the iacv with a multimeter. Done.

hamslice

Thought it looked pretty straight forward. One question...anybody know of the write up on how to bleed the coolant system. I've searched and can't seem to locate it on this forum. I was told there is one, so maybe someone knows of its existence.

hamslice

Basically I'm asking does anybody know how to bleed the coolant system. I've been looking for a while on here and on other forums and can't seem to get a straight answer. Just tell me step by step, where to look, what to loosen and what to re fill. Alright thanks!!

yohan420

there's a little bolt with a nipple on top of the thermostat housing, if you unscrew it cold it will come right out, you may see some coolant spill out, what appens is you unscrew it enough and then it will allow air to bleeed out the nipple in teh top.

looking from front of the car, at the far left of valve cover down a bit where the head meets the block, you'll see the coolant hose going into it.. beneath the tube going to the intake form valve cover. you can't miss it, i beleive its 10mm.

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