95 Ford Contour Stalling

hi I have a 1995 Ford Contour and I am at my end with it. My nephew is a mechanic at Mercedes and has tried to change the things that could be the cause but to no avail. maybe someone has had this problem in the past. It all started with a bad alternator we replaced that new battery to . The car is shaking at idle and in gear and stalls if no gas is given coming to a stop reversing and switching into gears. We have changed the following. Valve gasket cause oil was getting to spark plugs, plugs, wires, timeing belt, fuel filter, fuel pump, o2 sensor, pcv,air filter, and a few others but still nothing keeps happening any suggestions.
thanks

engine type, trans type would be helpful. thanks.

engine type, trans type would be helpful. thanks.
hi sorry
it is a 6cy duratech i think automatic trans.
thanks again

Try cleaning or replacing the IAC (Idle Air Control) valve. It's a common cause of idle problems on the Duratec.