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Old 10-03-2017, 09:52 AM   #1
zedjr10
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Idle surges after blocking air boost valve

I capped off my air boost valve and the inlet on air breather. Now my idle surges from 1k to 2k rpms after i accelerate and let off gas. It will do this a couple times then settle down and not do it again until i press the gas and let off. Anyone know what is causing this? If i turn AC on it does this continously. Could this be a problem with my IACV?

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Old 10-03-2017, 06:25 PM   #2
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I replaced my IACV and it still idle surges when ac is cut on. The surge goes up to 1800 rpms about and then back down to 1k and over and over continously until i cut off AC.
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Old 10-03-2017, 06:31 PM   #3
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FITV, how's it?
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Old 10-03-2017, 07:50 PM   #4
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Bad idle valve or vacuum leak.
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Old 10-03-2017, 07:55 PM   #5
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Quote:
Originally Posted by Jon View Post
FITV, how's it?
I just changed that also. Problem is the same. IT actually happens when fans turn on and only when fans turn on. AC just happens to turn them on. When i reconnect my Air boost valve the problem goes away. Maybe the ABV has the vacuum leak?
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Old 10-03-2017, 07:57 PM   #6
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Quote:
Originally Posted by F22Chris View Post
Bad idle valve or vacuum leak.
I replaced the IACV with one form the junkyard. AM thinking it has to be a vacuum leak somewhere. I have sprayed carb cleaner everywhere i can think of. Maybe the Air boost valve is leaking as when i reconnect the ABV back to its oem vacuum lines the problem goes away.
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Old 10-03-2017, 08:49 PM   #7
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Update. If i leave the vacuum inlet open on ABV and the fans cuts on the idle starts to surge but if i immediately put my finger over open inlet the idle returns to normal immediately even with the fans running. I am thinking now it is something electrical tied into the ecm. I read something about some main relay. Which i don't even know what it does. ANyone got any ideals?
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Old 10-04-2017, 03:04 AM   #8
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I read other people have this same issue when just blocking vacuum inlets with plug. Now me thinks the only way to delete the abv is with a plate. Anyone confirm this?
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Old 10-04-2017, 08:18 AM   #9
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I'm pretty sure that's the best way to delete the abv.
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Old 10-05-2017, 03:06 AM   #10
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i wonder why it does that, it is not the physics of the plenum as when i put finger on and then remove the fans are still running but it idles normal, Got to be electrical connected somehow, Maybe between the map sensor as it reads the pressure and then passes a signal on. SO the change tells the iacv to act differently. I really don't get it. AS what is the change when blocking of. I was thinking the diaphragm is cracked in abv(2 i have) and it sucks in air from outside, rather than thru a restricted vacuum. Or blocking off vacuum on air breather causes a different pressure reading and changes the readings of map sensor. AM guessing here. Does the abv somehow operate something else than i am not aware of.
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Old 10-05-2017, 09:10 AM   #11
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Quote:
Originally Posted by zedjr10 View Post
i wonder why it does that, it is not the physics of the plenum as when i put finger on and then remove the fans are still running but it idles normal, Got to be electrical connected somehow, Maybe between the map sensor as it reads the pressure and then passes a signal on. SO the change tells the iacv to act differently. I really don't get it. AS what is the change when blocking of. I was thinking the diaphragm is cracked in abv(2 i have) and it sucks in air from outside, rather than thru a restricted vacuum. Or blocking off vacuum on air breather causes a different pressure reading and changes the readings of map sensor. AM guessing here. Does the abv somehow operate something else than i am not aware of.
You are looking way too far into this one.

The air boost valve is a simple device. IIRC it's open when no vacuum is applied to allow more air into the engine during starting. When vacuum is applied, it should be closed off.

You should not feel vacuum when you put your finger on the ABV nipple. If you do, there is a leak into your manifold = vacuum leak.

Main relay simply supplies power to the fuel pump, ecu, coil, and injectors. If it wasn't working, your car would not start. It's actually two relays and the fuel pump side is the one that typically dies due to a broken solder connection.
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Old 10-06-2017, 06:09 AM   #12
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haha yeah maybe i am. Just was curious how that worked and why it surges when i do that.
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