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Kuhaku

High idle loss of A/C R34 GTT

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Hi All,

Been going through the idle forum posts, does anyone know some key areas to look or have experienced this once before with high idle 1500-1600 rpms and during this high idle I lose the air/con (heater works fine) as 1 to 1 with the issue resetting the Nistune ECU doesn't do anything it starts off at 1k rpms and slowly creeps up to 1500-1600 after a minute, air con doesn't engage at all can't hear the clutch kick in at all, RB25DET NEO with a cheap front plenum so no correct water gallery for the cold morning starts but this shouldn't be impacting the symptoms I am having though it is on the to do list to get it changed out, adjusting the IAC screw doesn't change the idle at all and clamping the hose doesn't change anything either, no obvious vacuum leaks side note is it is slightly hesitant on throttle input but I mean only very slightly once moving or warm there is no hesitation and drives fine with no miss firing etc, this has happen to me once previously and the issue stayed around for a couple of weeks then vanished and A/C started working again at the same time, this again seems to be that case.

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Do you have an air valve at the AC compressor?  On some cars they provide an idle up when the compressor comes on.  Could be the sort of thing that might cause such symptoms.  I don't think that Neo AC compressors are supposed to have that valve though.

If I had to guess, I would suggest that your IACV is filthy and needs a complete disassemble and clean with solvent.

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20 minutes ago, GTSBoy said:

Do you have an air valve at the AC compressor?  On some cars they provide an idle up when the compressor comes on.  Could be the sort of thing that might cause such symptoms.  I don't think that Neo AC compressors are supposed to have that valve though.

If I had to guess, I would suggest that your IACV is filthy and needs a complete disassemble and clean with solvent.

Thank you GTSBoy I will organise a new gasket for the IACV and give it a shot, highly likely to be the answer I will update the post if it is, thank you :) I do have a R33 IACV laying around so I wonder if something is dead if I can swap it out with that since I am not using the cold start water galleries featured in the NEO at the moment I will compare the slots.

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I don't think they (R33/4 IACVs) swap.

Mine (Neo one) had to be thoroughly cleaned recently because, for years, it had occasionally done weird shit like hold the idle at 1500 or so rpm in traffic, or blip the idle like a race car.  It got really bad, to the point where I couldn't put up with it any more.  It was all because the IACV was dirty enough to get stuck sometimes but not all the time and the ECU didn't have control over the IACV when it was playing up/sticky, but had control most of the time.

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Cleaned out my IACV sadly hasn't helped or changed anything for me, def was build up, was good to do so I have found some previous owner interesting adjustments, for starters it is actually a RB25 Non-NEO not a RB25 NEO IACV. Now I found this disconnected plug this in under the plenum on the intake side, would anyone know what this plug is doing, is the IACV meant to be connected here I can't tell, if this grey plug leads all the way to the A/C would make alot of sense why my A/C is loss and my idle is on a constant high but don't want to plug this in without knowing what is actually does.

20190316_161012.thumb.jpg.6d0145bf0d8e3e88f3a815d4fd6cb2da.jpg

 

20190316_122749.thumb.jpg.8228fffd3f170d8adee0b5243273b266.jpg

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To answer my own question looks like that cable is ran to the traction control on the throttle body which isn't connected as it is running a R33 throttle body, so there is something else that isn't reporting back to the ECU correctly that is causing my idle issues, do I require a Nistune license to view voltages and basic diagnostics information from the ECU or do I have to fork out the $200 + purchasing a consult cable.

Edited by Kuhaku

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On my rb25 (not neo) reason for high Idle turned out to be a boost leak. Unblocled hose nipple under the oem throttle body fitted to a Freddy intake with an adapter plate. Couldnt see it as its hidden under the throttle body. Found it only when leak tested my boost pipes with a compressor. Worth a shot maybe

  • Thanks 1

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7 hours ago, Kuhaku said:

To answer my own question looks like that cable is ran to the traction control on the throttle body which isn't connected as it is running a R33 throttle body, so there is something else that isn't reporting back to the ECU correctly that is causing my idle issues, do I require a Nistune license to view voltages and basic diagnostics information from the ECU or do I have to fork out the $200 + purchasing a consult cable.

No you don't have to. You can download the Nistune software from their Software Downloads page and you will get free 4 day trail. Then get a nissan consult cable from ebay or something. Check what your throttle position is on the TPS. You can check it on the nistune software

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4 hours ago, thebe said:

On my rb25 (not neo) reason for high Idle turned out to be a boost leak. Unblocled hose nipple under the oem throttle body fitted to a Freddy intake with an adapter plate. Couldnt see it as its hidden under the throttle body. Found it only when leak tested my boost pipes with a compressor. Worth a shot maybe

Right on the money mate how would you suggest blocking it? Interesting how this only now starting to be an issue when this plenum was installed by the previous owner well over 3 years ago and I don't imagine this ever being blocked. I will have to correctly block it and see how it goes.

23 minutes ago, RB25Detonator said:

No you don't have to. You can download the Nistune software from their Software Downloads page and you will get free 4 day trail. Then get a nissan consult cable from ebay or something. Check what your throttle position is on the TPS. You can check it on the nistune software

Thanks will give it a shot.

 

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I have ordered silicon blanking caps for the nozzle, will be handy for the future anyway if anything else pops up, also ordered the Consult cable. Will update once everything arrives and let the forum know if everything runs after this to help with anyone else if they're having the issue.

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I bought a set of silicone/rubber blocking-thingies. Cant remember the correct size but iirc it is smaller than your usual boost nipple on wastegates, bypasses and fprs. Screenshot_20190319-143608__01.jpeg

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