Somebody correct me if I'm wrong but I don't think the idle can be adjusted.
If I may, you sound like you are experience the same symptoms everyone else on this board has with their zetec.
It seems like the idle is too low. There have been several suggestions made on the remedy. New fuel filter, new tensioner pulley, new plugs, new wires, new coil pack...
Different things work for different people. Provide more details for the other guys about your car. Miles, model, routine maintanence performed, etc...
