Biss adjustment/ IAC position

[97gsxturbo97]

First off, I searched and have not found an answer to a few questions. I have DSMlink so I can monitor IAC position. When I adjust the biss do I want to ground the diagnostics or timing or both at the same time to adjust the biss. Also, does anyone know the IAC position it is suppose to be set at. Someone told me 30. Without grounding anything with DSMlink the Iac is around 30 but it keeps jumping. WHen I ground DIAG and Timing it is around 9 or 10 and the idle drops to around 600 rpm. Do I want the idle to be at 750 when I ground the Diag and Timing connector or is it suppose to go that low? Thats what I wasn't too clear about. Thanks for your help. Surprisingly VFAQ doesnt even mention these specifics.

 

[ndsti]

Unplug the IAC, adjust the BISS to where you want your idle to be, plug the IAC back in and your good to go.

This is assuming that you have the proper base timing and no boost leaks.

 

[habitatguy187]

The easiest way to adjust the BISS is to shut the car off, adjust it, turn the car back on, see where it's at. I can't help you with the IAC.

 

[97gsxturbo97]

The whole point of this is too make sure that the IAC is not too far in either direction of its range so it can compensate correctly. The two methods you guys proposed will screw up what I am trying to do. When the car is off the IAC is completely closed and if I unplug it while the car is running it will just get stuck in whatever position it was in.

 

[blazebolt]

You do not need to ground timing or diag. Below is from the dsmlink forum.

2G Tuning : B.I.S.S. (Base Idle Set Screw)

--------------------------------------------------------------------------------

In order to properly adjust the B.I.S.S. your car must be idling at operating temperature.

Log the following values:
-RPM (~ your DSMLink setting)
-ISCPosition (~30 at idle)
-LearnedIdleAdjust (~140 at idle)

Adjust the B.I.S.S. to achive the above values. LearnedIdleAdjust is slow to react, so wait 5-10 minutes between your adjustments. Be patient.

Tighten B.I.S.S. or Clockwise
- Decreases RPM
- Increases ISCPosition, and LearnedIdleAdjust.

Loosen B.I.S.S. or Counter Clockwise
- Increases RPM
- Decreases ISCPosition, and LearnedIdleAdjust.

 

[steve]

I have DSMlink so I can monitor IAC position.

When I adjust the biss do I want to ground the diagnostics or timing or both at the same time to adjust the biss.

Also, does anyone know the IAC position it is suppose to be set at. Someone told me 30. Without grounding anything with DSMlink the Iac is around 30 but it keeps jumping.

When I ground DIAG and Timing it is around 9 or 10 and the idle drops to around 600 rpm. Do I want the idle to be at 750 when I ground the Diag and Timing connector or is it suppose to go that low?

With DSMLink you ground both from UI. That puts the ECU into BISS adjustment mode.

While these are grounded you adjust the BISS to get a 750 RPM idle speed. The ECU is locking the ISC to about 10 steps while it's in this mode. Once you unground the signals the ISC steps should be as blazebolt posted. If they aren't after correctly setting the BISS, you can tweek the BISS without grounding the settings to hit these values.

Make sure to check the ISC coil resistances and perhaps clean the pintle before starting the adjustment. It's isn't going to work very well if you have a bad ISC.

 

[Number_4_]

With DSMLink you ground both from UI. That puts the ECU into BISS adjustment mode.

While these are grounded you adjust the BISS to get a 750 RPM idle speed. The ECU is locking the ISC to about 10 steps while it's in this mode. Once you unground the signals the ISC steps should be as blazebolt posted. If they aren't after correctly setting the BISS, you can tweek the BISS without grounding the settings to hit these values.

Make sure to check the ISC coil resistances and perhaps clean the pintle before starting the adjustment. It's isn't going to work very well if you have a bad ISC.

But do you still need to ground the timing pin in the engine bay also, or just click the 2 buttons in dsmlink. Your saying if you have dsmlink you don't need to physically ground anything, just use the ui in dsmlink? I have a gvr4 that I'm trying to set the idle on after installing a new ISC. Thanks for any info.

 

[Majikterror]

Is there directions for use with EVOscan? Don't want hi-jack a thread but not everyone has DSMlink and I read that it can be done with EVOscan as well.

You do not need to ground timing or diag. Below is from the dsmlink forum.

2G Tuning : B.I.S.S. (Base Idle Set Screw)

--------------------------------------------------------------------------------

In order to properly adjust the B.I.S.S. your car must be idling at operating temperature.

Log the following values:
-RPM (~ your DSMLink setting)
-ISCPosition (~30 at idle)
-LearnedIdleAdjust (~140 at idle)

Adjust the B.I.S.S. to achive the above values. LearnedIdleAdjust is slow to react, so wait 5-10 minutes between your adjustments. Be patient.

Tighten B.I.S.S. or Clockwise
- Decreases RPM
- Increases ISCPosition, and LearnedIdleAdjust.

Loosen B.I.S.S. or Counter Clockwise
- Increases RPM
- Decreases ISCPosition, and LearnedIdleAdjust.

 

[davidalindsey]

You have to center the ISC if a new one is installed.
You have to put the ecu in ISC adjust mode with a logger/scantool.
(Called Speed Adj. Screw Mode in EvoScan)

 

[KC2RPM]

when your making adjustments, is it best to have the engine at max operating temperature?

 

[davidalindsey]

when your making adjustments, is it best to have the engine at max operating temperature?

Yes the engine should be at normal operating temperature.

 

[BoostFrenzy]

If you are having difficulty adjusting your BISS to get your ISC position correct, follow these steps that I made. Especially good for when you ground both and your car dies like mine was.

DSMTuners Link