SR20DET Idle Hunt Issue

[Kenneth Yu]

HI LinkECU,

I am at wits end and so is my tuner on this idle hunt issue. Vacuum has been smoke tested and timing has been verified on a timing gun..... Any help would be appreciated....

On warmup and enrichment, it is normal, it just doesn't ever settle down.

Logs and Tune attached. Any help would be great...

NissanS13nonvtc-S14-15-G4X-Ken-yu-8-29-23 (2).zip

[DerekAE86]

If you've run out of attachment space here use a cloud service like Google drive to share your tune and log

[Vaughan]

Your TPS value is at 1.7% and so none of the idle control stuff is kicking in. Have you calibrated your TPS properly or is your throttle body not shutting properly?

[Kenneth Yu]

C

3 hours ago, DerekAE86 said:

If you've run out of attachment space here use a cloud service like Google drive to share your tune and log

Ahhh got it....

2 hours ago, Vaughan said:

Your TPS value is at 1.7% and so none of the idle control stuff is kicking in. Have you calibrated your TPS properly or is your throttle body not shutting properly?

My tuner suggested I open it, but didn't tell me to recal before trying again. I will give it a try.... Should at idle, the throttle plate be completely shut?

[Vaughan]

6 minutes ago, Kenneth Yu said:

My tuner suggested I open it, but didn't tell me to recal before trying again. I will give it a try.... Should at idle, the throttle plate be completely shut?

For cable throttle setups the TPS value in the ECU should be 0% when you are completely off the throttle

[koracing]

Depending on what your idle control motor duty cycle is fully warm will somewhat dictate where the throttle blade needs to be set at for it's "zero" position.  Fully closed physically is ususally not the right setting unless you have some other idle air bleed or throttle bypass passage on the throttle body.

[Kenneth Yu]

14 hours ago, Vaughan said:

For cable throttle setups the TPS value in the ECU should be 0% when you are completely off the throttle

So I fully shut it and it still does the same thing... I found an old thread to help me check continuity in the IACV to see if I am getting a signal to the ecu.... 
In general I wonder with all the aftermarket cooling, I am thinking the IACV doesn't really work. Reading through the manual, the coolant temp is 174F is considered as "warmed up", but with the cool california weather, running distilled water only, and more efficient fans with the stock clutch fan, I will only get around 155F. Under hard driving I would only see about 165F usually. Could this be a factor?

1 hour ago, koracing said:

Depending on what your idle control motor duty cycle is fully warm will somewhat dictate where the throttle blade needs to be set at for it's "zero" position.  Fully closed physically is ususally not the right setting unless you have some other idle air bleed or throttle bypass passage on the throttle body.

Nissan's have this valve that use some wax thing to dictate how much air to let into the intake. This valve bypasses the throttle butterfly plate and goes straight into this valve. But like I said, "warmed up" is considered 174F, but I am usually way under that for light loads.

[koracing]

Try blocking the IACV off and see if it makes a difference.  

[Kenneth Yu]

16 minutes ago, koracing said:

Try blocking the IACV off and see if it makes a difference.  

Yeah thats my next step, but it has some coolant hoses and I gotta get a block off plate and all that.... never look forward to messing with coolant

[DerekAE86]

2 hours ago, Kenneth Yu said:

So I fully shut it and it still does the same thing... I found an old thread to help me check continuity in the IACV to see if I am getting a signal to the ecu.... 
In general I wonder with all the aftermarket cooling, I am thinking the IACV doesn't really work. Reading through the manual, the coolant temp is 174F is considered as "warmed up", but with the cool california weather, running distilled water only, and more efficient fans with the stock clutch fan, I will only get around 155F. Under hard driving I would only see about 165F usually. Could this be a factor?

Vaughan wasn't suggesting you shut the throttle. He was saying to leave your throttle slightly cracked as the Tuner said, but recalibrate the TPS so in this slightly cracked position it reads 0% so all the ECU Idle Control functions can operate and improve your idle.

Also 165f/73c sounds very cold for full temp conditions. Are you sure your temp sensor has the correct calibration assigned to it?

[Kenneth Yu]

8 hours ago, DerekAE86 said:

Vaughan wasn't suggesting you shut the throttle. He was saying to leave your throttle slightly cracked as the Tuner said, but recalibrate the TPS so in this slightly cracked position it reads 0% so all the ECU Idle Control functions can operate and improve your idle.

Also 165f/73c sounds very cold for full temp conditions. Are you sure your temp sensor has the correct calibration assigned to it?

Coming out of the neck is about 80c and after radiator its 154F....... have a high capacity clutch fan and a 3 row koyo rad witha 1.1 bar cap

[DerekAE86]

I would still confirm you have the right cal for your sensor.

My car sits at 93degc (200f) at full temp/load wiith huge Koyo rad and twin electric fans.
Which is exactly where the factory service manual says it'll cycle the fans on and off.

[jdniss]

My SR sits at 68~78deg C water temp at full temp/load with a Koyo N-Flow dual pass radiator and GKTech clutch fan ~ 73deg sounds somewhat cold but not unreasonable.

Even my SR track car barely dipped into the high 90's deg C water temp at full noise, same radiator and fan setup - and that was after a 15min Sprint.

They were both measured by the factory Nissan Coolant Temp sender - along with a Defi coolant temp sender that's consistently within 3deg of these numbers.


@Kenneth Yu is there a big exhaust cam in the car..?
There's some pretty killer waves in the MAP signal regardless of throttle position - has the MAP sensor been calibrated?

[Vaughan]

My Stagea sits at around 76degC with an OE radiator and thermostat for reference

[Kenneth Yu]

23 hours ago, jdniss said:

My SR sits at 68~78deg C water temp at full temp/load with a Koyo N-Flow dual pass radiator and GKTech clutch fan ~ 73deg sounds somewhat cold but not unreasonable.

Even my SR track car barely dipped into the high 90's deg C water temp at full noise, same radiator and fan setup - and that was after a 15min Sprint.

They were both measured by the factory Nissan Coolant Temp sender - along with a Defi coolant temp sender that's consistently within 3deg of these numbers.


@Kenneth Yu is there a big exhaust cam in the car..?
There's some pretty killer waves in the MAP signal regardless of throttle position - has the MAP sensor been calibrated?

Yeah. Stage 3 hkscams 264 intake 272 exhaust. There spread the lobes 2.5 degrees retarding intake and 2.5 degrees advance exhaust on jwt cam gears.   Also granted its a cool 75 drgrees where i live.  

Yes map is calibrated.  Does a twin plate orc mess up the idle as well?

[KennyJ]

sr's have that thermostat extra idle thing on the throttle body, which i most times remove.
engines with cams need some throttle opening most times- reset tps calibration when done
i usually give them just a little extra opening and temper them down with idle ignition control. to make them a little stronger on idle.

also the fact that it was hunting with idle control off means there are some weird things going on in the ignition and/or fuel map in those cell's
make a mixture map logging to check fueling , timing can be done visually in the map.
take care not to overlook heatsoak in the iat sensor 
also sr's tend to have a few % difference at 80°C to 90°C ect- but that would cause hunting

overshooting lambda control or idle control can cause this to- but not in your case here

[koracing]

7 hours ago, Wanderer said:

i usually give them just a little extra opening and temper them down with idle ignition control. to make them a little stronger on idle.

This on any car running larger cams is key for optimal smooth idle control I've found.

[Kenneth Yu]

For Idle ignition control, is there a map on it or anything? Cause i just see the option on and off

[Adamw]

It is closed loop.  So just the settings shown below.  In the latest firmware you can further make the target value come from a table instead of a single value but I would only add that complication for special cases such as ITB with no idle valve.