I had that, it's the COIL PACK. I suspected it because 2 cylinders went at exact same time. Run's real ruff, no power, act's like it's gonna stall. Changed coil and ran like a champ after. I think it's a common thing for these to go. Easy to change out.
2002 Windstar it's mid engine, just behind the intake; follow the spark plug wires. Very, very easy to change, only need minimum skill on cars. I'd buy the replacement first so you have it right there when you pull the old one. Look at the new one to see where the 7mm hex bolts are. First reach in (A little tight, but arms will fit around both sides of engine) an undo all three hex bolt, it will make it easy to disconnect thin wire connector and plug wire if you can move it around. Then unplug thin wire connector, I had to use needle noise in order to pinch the little tab that released the plug. Move the new coil back there pune plug one at a time, plug into the new immediately to get the righ socket. Pull old coil out when done. Plug in the thin wire connector. Move new coil over mounting screw holes. I had to unplug a few wires one at a time again to get them to lay right in order to get the coil to sit right. Put in hex bolt Very Very lightly! only snug, barly snug, or you'll bust it. Start the car and Vrrroom! runs like it's brand new! I had codes P0303, P0304, (Misfire 3&4 plug) from the free computer read at Auto Zone- along with P0171 & P0172. All codes gone after this coil replace. I don't know why Ford put such a crapy part that fails on there cars. Runs like a champ now. Good luck. Part $65 at auto zone.
Tim O.