SR20DE High Idle, Zombie AAC?

Engine, Transmission and related drivetrain.
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okayfine
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Re: SR20DE High Idle, Zombie AAC?

Post by okayfine » 18 Nov 2014 15:55

STILL dealing with this.

Used AAC installed. Everything connected, still have 1500+ idle.

Verified TPS settings.
Verified AAC voltage from ECU and ohm through the AAC.
Verified ECU Coolant Temp Sensor functions (so the ECU isn't thinking it's just cold all the time).
Opened heater valve to ensure hot coolant was circulating through the system, including through where the AAC grabs coolant in the loop.

With AAC disconnected, the air supply hose still pulls a vacuum with my thumb over the the end.

Removed the throttle body to inspect for any air openings I couldn't see with it attached. There's a boss on the bottom without a nipple tube, and I couldn't verify it was closed without removing it. Closed, and I plugged it anyway. Noticed a bare glimpse of daylight, so the TB butterfly isn't sealing perfectly in the TB bore. Tried to adjust it, couldn't really improve it. Reassembled and taped up the TB butterfly to the bore to prevent air leaking.

Started the engine with the TB taped, AAC plug disconnected, but AAC air supply hose connected. ~750idle, dropping to ~500 when it got warmer. Plugged in the AAC and ~1500+idle. :roll:
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Three B's Racing
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Re: SR20DE High Idle, Zombie AAC?

Post by Three B's Racing » 19 Nov 2014 11:39

okayfine wrote:STILL dealing with this.

Used AAC installed. Everything connected, still have 1500+ idle.

Verified TPS settings.
Verified AAC voltage from ECU and ohm through the AAC.
Verified ECU Coolant Temp Sensor functions (so the ECU isn't thinking it's just cold all the time).
Opened heater valve to ensure hot coolant was circulating through the system, including through where the AAC grabs coolant in the loop.

With AAC disconnected, the air supply hose still pulls a vacuum with my thumb over the the end.

Removed the throttle body to inspect for any air openings I couldn't see with it attached. There's a boss on the bottom without a nipple tube, and I couldn't verify it was closed without removing it. Closed, and I plugged it anyway. Noticed a bare glimpse of daylight, so the TB butterfly isn't sealing perfectly in the TB bore. Tried to adjust it, couldn't really improve it. Reassembled and taped up the TB butterfly to the bore to prevent air leaking.

Started the engine with the TB taped, AAC plug disconnected, but AAC air supply hose connected. ~750idle, dropping to ~500 when it got warmer. Plugged in the AAC and ~1500+idle. :roll:
SHIT!!! sorry to here that. The TB butterfly isn't supposed to sit perfectly in the bore. It is actually supposed to sit just off a total seal to keep it from sticking. My S14 throttle body has a Thermo-Element Stroke setup that is wax filled that controls the cold start and hot idle. Radiator water runs past this element and when the water gets hot the wax gets soft and causes the element stroke cam on the TB butterfly to slowly recede closing the TB up against that little butterfly adjustment nut and screw. Does your TB have this same setup? There are two marks on that element stroke cam, one for when it's cold and one when hot. These need to be set properly to achieve proper cold/hot idle.

Got this from my manual about IAC, hope it helps.

This system automatically controls engine idle speed to a specified
level. Idle speed is controlled through fine adjustment of the
amount of air which bypasses the throttle valve via IACV-AAC
valve. The IACV-AAC valve repeats ON/OFF operation according
to the signal sent from the ECM. The camshaft position sensor
detects the actual engine speed and sends a signal to the ECM.
The ECM then controls the ON/OFF time of the IACV-AAC valve
so that engine speed coincides with the target value memorized in
ECM. The target engine speed is the lowest speed at which the
engine can operate steadily. The optimum value stored in the ECM
is determined by taking into consideration various engine
conditions, such as during warm up, deceleration, and engine load.
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Re: SR20DE High Idle, Zombie AAC?

Post by duke » 19 Nov 2014 11:53

Man, a pair of SU's sounds pretty appealing right now eh? (sorry, I had to say it)
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Re: SR20DE High Idle, Zombie AAC?

Post by okayfine » 19 Nov 2014 12:07

duke wrote:Man, a pair of SU's sounds pretty appealing right now eh? (sorry, I had to say it)
Well, SUs sounded a lot better back when the L20BT was blowing smoke. It's a different battle now.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

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Re: SR20DE High Idle, Zombie AAC?

Post by okayfine » 19 Nov 2014 12:11

Three B's Racing wrote:Does your TB have this same setup?
Nope. It has coolant IN and OUT, but other than that just a couple vac ports (all capped), and the TPS off the side, of course. Throttle shaft is independent - no short/long marks/dots like the FSM suggests. I'll get a picture in a bit. Should have taken one when I had it off.

On the KA and such, there is a separate IACV. I have only AAC/FICD. FICD is the high-load idle (for when the A/C comes on) and is not hooked up.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

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Re: SR20DE High Idle, Zombie AAC?

Post by okayfine » 22 Nov 2014 13:27

Does this look like a standard S13 SR20DE throttle body to you?
IMG_6228.jpg
IMG_6228.jpg (205.29 KiB) Viewed 2950 times
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

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Re: SR20DE High Idle, Zombie AAC?

Post by okayfine » 22 Nov 2014 17:28

Buying another TB. S14 this time, so it'll have Lou's cold-start dealio on the TB itself. We'll see. There's gotta be an answer somewhere.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

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Re: SR20DE High Idle, Zombie AAC?

Post by spriso » 22 Nov 2014 19:10

Couple problems with the S14 throttle body Julian...

First, the throttle cable linkage is different, as the throttle body is mounted on the top of the intake plenum, instead of underneath on the S13.

S13 Throttle Body:

Image

S14 Throttle Body:

Image

Differences in linkage:

Image

The other thing to be wary about when buying S14/S15 throttle bodies is that the SR20DET version necks down to 54mm (instead of the 60mm that the NA engines have), a common swap for the DET guys is to put the NA throttle body on (which is why they are often missing on the DE engines):

Image

My recommendation would be to get the correct S13 throttle body so you don't have to kluge something together.

Michael
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Spriso Motorsports
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Re: SR20DE High Idle, Zombie AAC?

Post by finn » 23 Nov 2014 19:24

Have you checked your coolant temperature sensor?
'69 2dr KA24DET
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Re: SR20DE High Idle, Zombie AAC?

Post by okayfine » 24 Nov 2014 06:10

Yep. Power wire gets 4.7V with the engine running, the resistance starts out ~2400ohms and starts dropping as soon as the engine starts. About a minute into the test it as ~500ohms and I stopped. FSM spec is ~2000ohm ambient, ~200ohm normal running temp.
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Re: SR20DE High Idle, Zombie AAC?

Post by akara » 16 Jan 2015 22:22

The SR20 controls the idle speed at all times with the AAC valve and TPS. It's very easy to diagnose idle problems with this engine if you have access to a laptop and Nissan Consult adapter. The throttlebody should be closed, as the engine idles off of the air from the AAC bypass. The first thing I would do is check the TPS Idle flag with Consult. This flag is set when the ECU sees .35-.65 volts from the TPS sensor. Sometimes you have to do a little dance to get the SR20 ECU to recognize the TPS idle voltage. I usually have luck by warming it up, reving it up a couple times and then unplugging and replugging the TPS while it is running.
When the TPS is not set the engine will act as if you are just off throttle, and it will set timing to around 35 degrees. When the TPS Idle flag is set correctly the engine will actually control AAC duty cycle to adjust the idle. If you have a vacuum leak the ECU will pull the AAC duty cycle down to 0 and then will pull timing all the way down to 5 degrees in order to try and control the idle. After you have set the TPS correctly set you can go ahead and adjust the AAC idle screw until you see the timing stay at 15 degrees at idle or when the AAC duty cycle is around 50%, this is where they like to idle the best.
As long as your TPS and AAC are functional and you dont have any major vacuum leaks the Idle system is pretty forgiving.

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Re: SR20DE High Idle, Zombie AAC?

Post by alsct1 » 27 Sep 2018 15:05

Hello, just wondering if you ended up finding a solution to this problem? I’m having the exact same issue with a stock s15 SR20DE. If I unplug the aac unit it will idol perfectly. I can also adjust the TPS while the car is running and it will sometimes correct the idol, soon as I restart the car again the idol goes back to 1500 or so. Any input would be appreciated.

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