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High idle issues

C.callander
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C.callander Apprentice

C.callander

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Hey guys i recently swapped my r33 from rb20e to rb25de s2, now it runs n drives but i cant get my idle lower then 1500, ive looked for intake leaks by spraying start ya bastard to see if it picks up and i get nothing so i replaced the intake gasket set and rechecked for leaks and still nothing, ive cleaned the iacv nothin, ive wound out the idle screw, removed the iacv plug nothing, turned the cas to see if its that but no, but also  when removing the intake i got water in the engine so i blew it out then removed the plugs and wound it over to clear it out its fine now but smokes abit now any ideas on both my problems would be great cheers 

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C.callander Apprentice

C.callander

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  On 10/04/2022 at 3:15 AM, BK said:

You mean in right ? Out raises the idle speed.

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Haha yea man I only mentioned it so everyone knows what I’ve tried, its wound all the way in now still the lowest rpm is 1500 

C.callander Apprentice

C.callander

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  On 10/04/2022 at 3:43 AM, BK said:

Nearly always comes back to a vacuum leak somewhere.

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Yea thats my thoughts but should have jumped in rpm squirting the start ya bastard around but it didn’t 

BK Grand Master

BK

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  On 10/04/2022 at 4:35 AM, C.callander said:

Yea thats my thoughts but should have jumped in rpm squirting the start ya bastard around but it didn’t 

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You mean it should have dropped rpm, but maybe you just haven't found it yet. Keep trying everywhere like injectors, brake booster, etc. Good luck.

joshuaho96 Veteran

joshuaho96

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  On 10/04/2022 at 7:00 AM, C.callander said:

So I’ve found no leaks but I’ve found the earth to my iacv isn’t working, is it an constant earth to the battery or does it get its earth from the ecu 

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IACV/AAC valve is normally closed. So without power it should be fully closed. Fix it but that's probably not your problem.

C.callander Apprentice

C.callander

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  On 10/04/2022 at 7:35 AM, joshuaho96 said:

IACV/AAC valve is normally closed. So without power it should be fully closed. Fix it but that's probably not your problem.

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Only reason I think its iacv is cause of this 

 

 

GTSBoy Grand Master

GTSBoy

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Constant 12V means that the other side (the earth side) is the switched side. If there is no earth there, then the switching device is not switching it on.

The IACV is not just a simple device though (ie, not just on-off). Look at the manual for what you can expect to see when it is working, and what you might see when it is not.

joshuaho96 Veteran

joshuaho96

Posted
Posted (edited)
  On 10/04/2022 at 7:57 AM, C.callander said:

Only reason I think its iacv is cause of this 

IMG_0778.MOV 26.76 MB · 3 downloads  

 

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The hose you clamped is not just for the AAC valve, there's also an intake air regulator/cold start valve in there that affects your idle:

image.thumb.png.55ba691b2a30e7dabb8b8006b3164291.png

Verify that your cold start valve is actually getting power and closing after some time. To some extent this is just guessing because your intake is clearly not stock and it's unclear whether the routing of your vacuum lines is still the same as factory especially because your crankcase vent lines are gone. I also must emphasize that as a general rule once you set the AAC idle screw on an engine that is otherwise mechanically perfect (no leaks/etc) you should never ever touch it again. Your idle getting out of whack is never going to be fixed by touching a screw that has extremely limited control authority, and it is never a good idea to band-aid over some issue with air control by touching that idle screw even if it does work.

Edited by joshuaho96

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