Honda Civic / Del Sol (1992 - 2000) EG/EH/EJ/EK/EM1 Discussion

Iacv: DIY testing

Old 01-19-2008, 09:42 PM
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Default Iacv: DIY testing

I have now come into ownership of 3 bad d16y8 iacv's. I really found it hard to belive that I have luck that is that my dad and I devised a way to test iacv's without having to bolt them on.

Iacv #1:
This one came with my manifold setup. From the first day i owned this one it gave me an issue. Whenever the car was idling I could hold the gas at any rpm and it would 2step. The idle was a constant but if i ever opened the screw up to raise the idle it would begin misfiring instead of idling higher. About a week into my car running the fitv got stuck closed. I think this one was so bad that the circuit through the solenoid wasn't even being completed which gave me the symptoms of an unplugged iacv.

Iacv #2:
Bought for $7 from N7J3H2C on this site...he's a good friend of mine. His car has sat dorment since july and the iacv worked when he pulled the motor out. While I changed this one I routed my coolant lines passed the stuck closed fitv so the car would idle when it was cold. I put iacv on my car and it idled fine when it was cold, as expected, but then began to idle really high. This sucked because I was going to inspection. It idled at 2k all through inspection, making it impossible to stick the sniffer in my exhaust and get an accurate reading. By the time I got home from the inspection station my idle was loping.

Iacv #3:
I was given a d16z6 iacv for free because supposedly it uses the same bolt pattern as a d16y8 iacv...which it does, but the plug is not located in the same place and a piece of the y8 manifold prevents it from being bolted on.

At this point, I was petty pissed off. My dad, being an electrical whiz, whips out the 92-95 civic manual and figures out how many volts it takes for the solenoin on the iacv to open the valve. The book states that 12v will make the valve open fully. I brought all 3 iacv's in my current ownership inside and here's where the crazy DIY iacv testing begins.


2 electrical connectors
1 model electric train transformer
1 voltmeter
1 ohm/resistance meter

We connected the connectors to the voltmeter and found that at 80/100 on the transformer (speed marking) 12v was released. We then attached the connectors to each pin on the 2 pin iacv plug and we were answered with a loud buzz on iacvs 1 and 2 and no buzz on 3. On #3 we could actually see the valve open and stay open. To understand what this means, you have to know how a solenoid works:

A solenoid contains an alectromagnet that increases force when electricity is applied. This magnetic power opens the valve which is closed by a simple spring when the electricity is taken away. A solenoid tends to buzz when it's the buzzing is a bad thing.

We also tested the resistance of each iacv...I don't rmember what each individual one was but the resistance is really 8-15 ohms maybe?

Iacv #4:
This one is a y8 iacv, it was packed in a box for a year. Picked it up for free this morning from a good friend...brought it home, tested it, got some buzzing, but the valve was still opening. Apparently this one is on its way out but still works. I haven't gotten the chance to throw it on yet but.

One more thing...I really have no idea why coolant flows through the iacv. I originally thought that there was some kind of temperature sensor in there to tell the ecu when the car was at operating so the iacv would open....but the ecu gets the signal from the coolant temp sensor. All I can think of is that the coolnt keeps the air in there warm which would also explain why iacvs only work at operating temperature.

Thanks for reading, I'll keep this updated.
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Old 07-19-2019, 05:13 AM
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Default Re: Iacv: DIY testing

This post got zero love, but I just want you to know that it was very helpful to me when I just recently had to inspect mine and test for proper operation (and what behaviour to expect). Thank you!!
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