Breather on IAC? (should it be routed to intake pipe insead?)

scottiedawg66

New Member
Apr 1, 2005
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Hello,
I am curious if my IAC can cause a boost leak by having a breather on it rather than being plumbed back into the intake pipe? I assume this would cause a boost leak unless the IAC can get 100% sealed under boost, which I doubt. Any thoughts?
 

becauseican

Supramania Contributor
Mar 31, 2005
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Using a small K&N style fliter on the IACV is a common way to do it. It will not cause a boost leak, there is a oneway valve in the manifold under the valve, so unless that valve is broken, torn or put in backward, it shouldnt leek.
 

Evilempire1.3JZ-GTE

SF what a waste of supras
Jun 22, 2006
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I used a K&N Mini breather it will not hurt a MAP tuned car.
You could even have a boost leak on a JDM JZ engine it will not hurt the engine like the AFM metered oem ECU 7Ms you will still be able to drive the car with no problem but with a boost leak I think the JZ only makes ~200-220 crank HP So you still might want to fix it.

If it uses an AFM behind the filter then you can not have any breather in the system to open air or you can not have an external BOV because it meters AFR based on the AFM.
 

Evilempire1.3JZ-GTE

SF what a waste of supras
Jun 22, 2006
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Would you like a picture of mine ?
I could prob also dig up some P#s
You have to bend the water tube down just a tiny bit to clear the breather but there is nothing wrong with it infact it will help your car breath better on idle instead of it pulling the air through a long tube feeding off the intake.
 

scottiedawg66

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Apr 1, 2005
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i have the breather mounted directly to the IAC and my idle is too high (1400 rpm) I am assuming that my IAC is stuck open right now, but I would not be too surprised if that breather was also just letting too much air in? Any thoughts on this? Any one else just run a breather right from the IAC with basically no hoses? I cannot fit a breather on the turbo side of the engine where the stock tube runs since my single is pretty close to the valve covers and will melt anything I put over there. When I get home I think Im gonna run a line into my catch can from the IAC and see if that lowers my idle, i'll post up my findings.
 

Supra-Man18

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Nov 24, 2007
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scottiedawg66;1289101 said:
i have the breather mounted directly to the IAC and my idle is too high (1400 rpm) I am assuming that my IAC is stuck open right now, but I would not be too surprised if that breather was also just letting too much air in? Any thoughts on this? Any one else just run a breather right from the IAC with basically no hoses? I cannot fit a breather on the turbo side of the engine where the stock tube runs since my single is pretty close to the valve covers and will melt anything I put over there. When I get home I think Im gonna run a line into my catch can from the IAC and see if that lowers my idle, i'll post up my findings.


I dont think that has anything to do with your idle being up so high.. I Jus routed mine to the intake recently and Didnt really notice much diff but a smoother idle.. Maybe you have a vaccuum leak of somwhere ?
 

afracer

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Sep 1, 2007
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When the car is idling there's a shite load of air coming out of that pipe, when it goes vaccuum (after a rev) it sucks air in. So definitely have a filter on it if you run it like that, or simply route it back into the intake, the car should idle better that way as others have said. In my case it wouldn't even idle without it hooked into the intake.
 

scottiedawg66

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Apr 1, 2005
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that was my initial thought as well...but after a double check of vac lines it seems that valve is just stuck open. Still yet to work on it since i had to go get some spring skiing this weekend.
 

86_sports_1jz

slow 700hp build...
Aug 27, 2006
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i couldn't fit a breather on mine either and i didn't feel like bending anything so i just clamped a piece of wired screen, a pantihose, another piece of wired screen and another pantihose over it. just by layering all that stuff over the valve it seems to be working like a filter and i've had no problems