Why is a 1996 Windstar 38L 108000 miles missing badly when hot at idle with check engine light on and running rich and runs good when cold and at highway speed?

Answer 1

Connect a diagnostic code reader to find out what's going on. That's the only way you'll know for certain. It could be something as simple as a bad air filter or oxygen sensor but the computer diagnostics will tell you what code has been stored.