2003 ford windstar turning off

Is your check engine light coming on. Also, when's the last time you had a tune up? And check all of your vacuum lines for leaks, your fuel pressure regulator for leaks as well. Sometimes an intermittent fault in one/more of the sensors won't produce a code in the computer. So if you've done all of that and still have the same problem, you'll have to have a technician perform a drive test while reading all of your sensors live data in order to find the cause.