Cox Abele
10+ Year Contributor
- 485
- 54
- Jul 4, 2010
-
Roanoke,
Virginia
I've read the VFAQ and understand how to properly adjust the idle. I'm going to first set my throttle stop screw (since I have a 1g TB), adjust the TPS, idle the vehicle to operating temperature then start to make my adjustments. I know that the tutorials say to lock the IAC with a scan tool (for the 2g) which as you already know is an actuator in EvoScan. My quandary is this- Engaging the Idle Set actuator in EvoScan is supposed to lock the IAC in it's centered position to ensure maximum adjustment. (The link guys say to watch the IAC steps. I don't have my tuning computer in front of me right now, but I know that we can log IAC position, it's just called something else). Once the actuator is engaged at operating temperature, the IAC is locked and you begin to adjust the BISS screw.
But what about us automatic guys?
In a manual, if you snap the throttle shut, you have your foot on the clutch and RPMs crash to idle. The IAC maintains this just fine, and in theory should be dead centered (or close to it) as that's where the mechanical adjustment of the BISS has "calibrated" the IAC. However, with an automatic, you are still in gear with drag on the engine, demanding more air flow. ECUFlash has both a "Neutral/Park" target RPM and an "in gear" target rpm. If both are set equal, the IAC, in theory, would constantly be opened more (not centered) while idling in gear.
I'm theorizing here, but it's something for the brain to chew on. All of the tutorials suggest that it is optimal to set the BISS in neutral (5-speed and auto alike), but wouldn't theory dictate that setting the BISS while in gear in an automatic allow for more complete movement of the IAC rather than skewing it slightly to the side of open at all times?
But what about us automatic guys?
In a manual, if you snap the throttle shut, you have your foot on the clutch and RPMs crash to idle. The IAC maintains this just fine, and in theory should be dead centered (or close to it) as that's where the mechanical adjustment of the BISS has "calibrated" the IAC. However, with an automatic, you are still in gear with drag on the engine, demanding more air flow. ECUFlash has both a "Neutral/Park" target RPM and an "in gear" target rpm. If both are set equal, the IAC, in theory, would constantly be opened more (not centered) while idling in gear.
I'm theorizing here, but it's something for the brain to chew on. All of the tutorials suggest that it is optimal to set the BISS in neutral (5-speed and auto alike), but wouldn't theory dictate that setting the BISS while in gear in an automatic allow for more complete movement of the IAC rather than skewing it slightly to the side of open at all times?
