1999 discovery 1. idles high
#12
#13
You can move the plunger on the stepper all you want. When you turn the key on and off a few times it will reset itself. When you turn the key off the stepper closes, when you turn the key on it will back off a predetermined number of steps. The number of steps correspond to whatever was programmed into the ECU map as it relates to RPM's. The adaptive learning in the ECU will reset it's closed position. If it doesn't you can force it to adapt. I've done this many times and it works.
#16
Unplug the IAC. Turn key to on position, plug the IAC connector into the IAC. Turn key off. Repeat as needed.
It's really basic, the ECU closes the IAC when you shut the key off, thus shutting the idle circuit down killing the engine with no run on. When the key is turned to the on position the ECU runs the IAC out whatever number of steps the program dictates is idle speed(IIRC it about 21 steps). What you are forcing the ECU to do is re establish ZERO(closed is ZERO steps). An IAC can lose it's ability to accurately count steps, leaving the ECU to lose the ZERO step baseline. Closed = ZERO steps, idle speed is X number of steps out from ZERO. Temp plays a role here too, the ECU may increase or decrease the steps out according to temp. A sticky IAC will cause the ECU to lose ZERO, as the valve sticks but the ECU thinks it is still completing each step.
Make sure the IAC is clean before trying to force it to reset ZERO. If it still sticks any effort to force it to ZERO will be an exercise in futility.
It's really basic, the ECU closes the IAC when you shut the key off, thus shutting the idle circuit down killing the engine with no run on. When the key is turned to the on position the ECU runs the IAC out whatever number of steps the program dictates is idle speed(IIRC it about 21 steps). What you are forcing the ECU to do is re establish ZERO(closed is ZERO steps). An IAC can lose it's ability to accurately count steps, leaving the ECU to lose the ZERO step baseline. Closed = ZERO steps, idle speed is X number of steps out from ZERO. Temp plays a role here too, the ECU may increase or decrease the steps out according to temp. A sticky IAC will cause the ECU to lose ZERO, as the valve sticks but the ECU thinks it is still completing each step.
Make sure the IAC is clean before trying to force it to reset ZERO. If it still sticks any effort to force it to ZERO will be an exercise in futility.
#19
#20
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VikingDiesel
Discovery II
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02-24-2009 05:38 PM