The Vehicle Speed Sensor VSS instructs the IACV to open when the vehicle is moving and the throttle is closed (less than .49 volts)
The VSS also causes injector shutoff at 1500RPM or lower with throttle closed and VSS active.
It is entirely normal for the idle speed to increase to approx 1200RPM under these conditions.
The reason for this is to ease the change to 1st gear in the auto while coming to a stop.
Funny I had a Falcon that did this years ago and the dealer even didn't know of this feature. It is common in most older injection/auto setups. It probably still is.
Regards Philip A
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