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Old 01-25-2011, 11:38 PM   #1
prezarevo
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Default ALL THIS IACV talk

I'm just curious to know, say the idle air control valve were to be adjusted, would there be any gain from it? How bout a loss? Are you supposed to adjust it? How do you know when it's set rite? I honestly do not know if these are stupid questions or not..
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Old 01-25-2011, 11:53 PM   #2
Wrencher86
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Not stupid.... Uninformed?

On a non-drive-by-wire fuel injected car when you let off the gas the throttle plate closes completely. In order for the car to idle they manufactured a small port on either side of the plate and use an IACV assembly to connect the two. Inside the IACV is a small plunger that is driven by a motor. The plunger is moved back and forth to block off or clear the passage as needed for the amount of airflow required so that the car can idle. The motor is controlled by the ECU. The ECU uses data from all the other sensors (MAF, ECT, O2, etc.) to determine the amount of air the engine needs and then moves the plunger accordingly.

I can't quite remember exactly how it works but the ECU counts the number of polarity changes that happen inside the electric motor as the windings get switched and interprets that as counts or steps (the IACV is considered a stepper motor. Memory power seats work the same way). In the old days disconnecting the battery would make the car forget what "step" it was on and then when you tried to restart the car it would idle like crap until it learned where it was and where it needed to be.

There is no adjustment (the Evap sticker under the hood tells you this), the computer controls where it's set at. There is no power to be gained from messing with the IACV as it only controls the idle and is responsible for a very small port in the throttle body.
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Old 01-26-2011, 12:14 AM   #3
prezarevo
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well there is two screws. if theyre loosened and the top portion gets turned or turned to fast the car idles funky and then just flat out shuts off.
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Old 01-26-2011, 12:20 AM   #4
prezarevo
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Idk about the turbo models but i know the N/A has it. If you take a look in the abnormal idle thread you can see it on the pic i posted.
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Old 01-26-2011, 12:24 AM   #5
Wrencher86
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Are you talking about the bolts that hold the unit on? If they are loosened un-metered air enters the engine and it can't compensate for it.
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Old 01-26-2011, 12:40 AM   #6
ballitch
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Don't worry prezarevo, you CAN adjust your idle via the IACV, you can also adjust it using the throttle pos. sensor. But there is absolutely no performance gain that I can think of. Unless you launch it at every light, trying to impress people, I don't see it helping at all.



~Josh~
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Old 01-26-2011, 10:07 AM   #7
prezarevo
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Theres philips head screws on top of the valve. where the wire plugs in.
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