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Tech Talk Technical Discussion About The Nissan 240SX and Nissan Z Cars


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Old 08-07-2017, 02:45 PM   #1
nisileighty
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SR IACV delete

I'm searching for info on the IACV delete on the SR. I know this topic has been briefly discussed, but I would like to gain as much info possible.

Please only chime in if you have tried it or experience. Don't tell me it'll idle like crap if you haven't seen/done it before. Thanks all.
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Old 08-07-2017, 03:18 PM   #2
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Why do you want to delete it? I can tell you from experience that they are extremely nice to have. Even on a motec system you cant achieve a super clean idle without them.
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Old 08-07-2017, 03:29 PM   #3
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Quote:
Originally Posted by hanzbrady View Post
Why do you want to delete it? I can tell you from experience that they are extremely nice to have. Even on a motec system you cant achieve a super clean idle without them.


Reduce clutter, one less system that can go wrong, etc. The main reason is that even with the IACV and correct settings for my TPS, throttle plate, CAS, etc. I still can't get it to idle correctly (as in below 1200 rpm). I've tried 2 different IACV units and it does the same thing so I ruled out that it's not a bad unit. Ultimately, if my car can idle at a better RPM without it, I'll deal with slight fluctuations and occasional dips.
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Old 08-07-2017, 03:34 PM   #4
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Quote:
Originally Posted by nisileighty View Post
Reduce clutter, one less system that can go wrong, etc. The main reason is that even with the IACV and correct settings for my TPS, throttle plate, CAS, etc. I still can't get it to idle correctly (as in below 1200 rpm). I've tried 2 different IACV units and it does the same thing so I ruled out that it's not a bad unit. Ultimately, if my car can idle at a better RPM without it, I'll deal with slight fluctuations and occasional dips.
I'd look into figuring out why your idle is high before trying to band aid it by ripping systems out. Look for vacuum leaks and make sure that your set screw on the IACV is set properly. Also verify that the car is idling at 15* (if you're running a factory ECU.).

The IACV really only needs the 1 plug to function the coolant lines aren't needed. So you're not really getting rid of a lot of clutter, you only getting rid of what keeps your idle stable and keeps you car from stalling on decel.

Also I'd bet that removing the IACV on a factory system would result in a higher surging idle. Since right now its probably operating at close to 0% duty cycle trying to lower your idle.
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Old 08-07-2017, 03:47 PM   #5
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Quote:
Originally Posted by hanzbrady View Post
I'd look into figuring out why your idle is high before trying to band aid it by ripping systems out. Look for vacuum leaks and make sure that your set screw on the IACV is set properly. Also verify that the car is idling at 15* (if you're running a factory ECU.).



The IACV really only needs the 1 plug to function the coolant lines aren't needed. So you're not really getting rid of a lot of clutter, you only getting rid of what keeps your idle stable and keeps you car from stalling on decel.



Also I'd bet that removing the IACV on a factory system would result in a higher surging idle. Since right now its probably operating at close to 0% duty cycle trying to lower your idle.


Vacuum leaks have been tested and set screw have been properly set. CAS timing is set as well. These were all things I looked into before thinking about the IACV delete.

Coolant lines are already gone. But like I said, the clutter factor isn't the main reason.
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Old 08-07-2017, 03:49 PM   #6
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What's the AFR on idle? And im assuming that you did double check the timing at idle with a timing light? Is the car cammed?
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Old 08-07-2017, 04:48 PM   #7
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Quote:
Originally Posted by hanzbrady View Post
What's the AFR on idle? And im assuming that you did double check the timing at idle with a timing light? Is the car cammed?


Car is completely stock besides basic things like exhaust, intercooler, radiator, etc. Supporting mods basically.

AFR @ idle is right around 14.7.

Timing was checked with a timing light in timing mode.


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Old 08-07-2017, 04:50 PM   #8
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Quote:
Originally Posted by nisileighty View Post
Car is completely stock besides basic things like exhaust, intercooler, radiator, etc. Supporting mods basically.

AFR @ idle is right around 14.7.

Timing was checked with a timing light in timing mode.


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Check it outside of timing mode. It should be around 15 still, if it's more advanced the idle would be high.
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Old 08-07-2017, 05:03 PM   #9
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Originally Posted by hanzbrady View Post
Check it outside of timing mode. It should be around 15 still, if it's more advanced the idle would be high.


Will do. Gonna wait for it to cool down outside a little bit.
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Old 08-12-2017, 08:02 AM   #10
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the oem throttle body has a water passage. if you remove that water flow the idle will be higher because hot water is needed to expand a wax element in the throttle body to reduce idle speed.


You should be able to put your hand on the TB and kill the engine that way. If there are leaks anywhere it will keep running.
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Old 08-12-2017, 08:52 AM   #11
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The wax element is in the iacv. Coolant flow is needed through the iacv for the valve to close and settle the idle. That is why once your engine warms up, the idle drops. Coolant flow through the throttle body isn't necessary.
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Old 08-12-2017, 10:44 AM   #12
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The old I deleted my iacv coolant lines bit. Yeah, you should fix that.

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Old 08-13-2017, 12:23 PM   #13
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Quote:
Originally Posted by shanelach View Post
The wax element is in the iacv. Coolant flow is needed through the iacv for the valve to close and settle the idle. That is why once your engine warms up, the idle drops. Coolant flow through the throttle body isn't necessary.
oh man, its been so long. thanks for reminding me of that, are you sure though? Because I remember for years I ran the water in the TB for some reason. I thought I did anyways.
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