Adrian,
Won't turning the throttle stop screw affect the point at which the 'Throttle Position Switch' detects the 'closed' position? It's a while since I had the ICV version of engine (on a 1994 2L ECO), but I found unless there was enough 'travel' to ensure the throttle position switch was clearly triggered, when parts get warm and/or worn the 'stop position' may not be detected, and the floating rev scenario (as per your description) occurs.
In summary, the throttle stop screw should not be adjusted, without ohming out the closed and open positions of the throttle position switch and ensureing correct resistances/switching occurs. Haynes manual describe test method/values.
Won't turning the throttle stop screw affect the point at which the 'Throttle Position Switch' detects the 'closed' position? It's a while since I had the ICV version of engine (on a 1994 2L ECO), but I found unless there was enough 'travel' to ensure the throttle position switch was clearly triggered, when parts get warm and/or worn the 'stop position' may not be detected, and the floating rev scenario (as per your description) occurs.
In summary, the throttle stop screw should not be adjusted, without ohming out the closed and open positions of the throttle position switch and ensureing correct resistances/switching occurs. Haynes manual describe test method/values.