94-95 Mustangs Tuning Idle
From Mustang-Tech
Contents |
Overview
Does your car have a hunting idle? Stalling?
- Have your computer codes read
- Check for broken vacuum lines
- Clean your MAF
- Reset your idle
Setting Hot Idle (Without a tuner)
Method 1
If you set the idle with the IAC unplugged (you'd be setting the hot idle with it unplugged and with no accessories turned on), then the computer cant lower your idle later on. Remember, when setting the idle with the IAC unplugged, afterwards the computer can only raise your idle - it can't lower it (because you set the idle with no IAC input, to simulate it having zero duty cycle).
Note: If you have an automatic, set the idle a little high because when you shift to drive, the idle drops (you're going to be tinkering with it while it's in Park, where the idle is a couple hundred RPM higher).
Method 2
Make sure your TPS voltage is somewhere between 0.48v and 1.22v.
The stock idle settings are 1.5 turns from bottomed out on the ISC bleed screw and 1 full turn past 0.010" gap.
Tuning the ISC Dashpot[1]
It is critical that you have your ISC transfer and TB airflow properly setup before you begin messing with the dashpot, otherwise the ISC controller may not be in complete control of your idle
The dashpot functions slow down the transition to idle when the throttle is lifted.
- Decay
- Increasing decay rate speeds up the transition
- Decreasing decay rate slows down the transition
- Clips & Pre-Positions
- Decreasing airflow speeds up the transition
- Increasing airflow slows down the transition
Dashpot Pre-Position (x-DSDRPM y-AIR_#/M)
(dashpot_clip_1 in SCT) Lower the AIR_#/M in 10% increments to speed up throttle closing rate
ISC Dashpot Decay Rate
(aka FN879) Determines the dashpot (pre position airflow) bleed off rate according to the current dashpot value. During closed throttle mode the dashpot airflow is bled off by decrementing it in order to smooth the transition into rpm control by slowly eliminating the dashpot contribution to the idle airflow. Increase the decay rate in 10% increments to speed up decay
Dashpot Pre-Position Offset
(dashpot_preposition in SCT?) (aka DASPTO) An offset added to the final dashpot (pre position airflow) value in order to ensure some airflow during tip in or tip out. Typically set around 0.10 lb per min.
Lower the AIR_#/M in 10% increments to speed up throttle closing rate
Dashpot Maximum clip vs Vehicle Speed (MPH)
(dashpot_max_clip_VS in SCT) (aka FN882) The maximum dashpot (pre position airflow) allowed for a given rpm.
Lower the AIR_#/M in 10% increments to speed up throttle closing rate
Dashport Minimum Clip vs DASMPH
(dashpot_max_clip_RPM in SCT) Lower the AIR_#/M in 10% increments to speed up throttle closing rate
Throttle Body Airflow
The formula to calculate throttlebody airflow is: (MAFkghr * 2.2046226 / 60 = TB Air Flow)
