My '99 Exp. is in the shop having the #4 coil pack replaced. This is the second time. It was replaced under warranty (6,000 miles) the first time. No such luck this time (44000 miles). It seems the coil packs are too sensitive to moisture. Almost evertime I wash the Exp., I get a miss from wet coil packs until the engine warms up and burns off the moisture. I was in a heavy rainstorm Monday night and had the familiar coil pack miss Tuesday morning only the problem didn't go away. I know that the '99 has much less plastic inner lining in the front wheel wells than my '97 did. This could be letting too much water splashing in the engine compartment. Anybody else having similar problems with coil packs.

 

I believe I have read others who had the same problem with coil pack number 4. If I remember correctly, the heater hose with a worm type clamp under start up pressure leaks and drips on the coil pack number 4 and cause it to go bad. I would check the cooling system. Again, if my memory is correct, a pressure test will not show this leak. A "Ford" mechanic posted that during start up before the engine warms up, the coolant system pressure is real high. This is when that heater hose connection leaks. Hope this might help. You might check for older post on this topic or check with the Expedition Owners Group website which has a lot of useful information unique to the Expedition.

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1999 XLT,5.4,Wedgewood Blue,ClassIII Tow Hitches Front and Rear,K+N Air Filter,Bug Deflector,Window Vent Shades,Stainless Steel Door Edges