97 WINDSTAR 3.8 LTR 62,000 MILES THE VAN HAS A SKIP UNDER LOAD AND SETS #4 MISFIRE CODE PO304, CHECKED IGNITION SYSTEM REPLACED PLUGS AND WIRES DUE TO MILAGE. IF WE DISCONECT THE EGR VALVE THE SKIP GOES AWAY AND NO MISFIRE CODE IS SET. RUN TEST ON EGR SYSTEM A... Login to read more.