2001 Ford Expedition vehicle stalls when rain or wet(car wa

I've been having this prolem for quite sometime. It started out as stall during my trip to work one morning. It stalled on me while driving for about 20 mins into my commute into work. The vehilce just started to shake and it just lost all power at around 45-50 miles /hr. I pulled over onto the shoulder of the highway. Ater about 15 mins or so I got itStarted again. Got it to ford and they found that cioil pac #7 was bad, IAC was allso changed, throttle body was cleaned and MAP was also cleaned. It was running fine after this work was done. Then it started again and ford said to bring it again. They checked all the other ciols and everything looked fine. I told them it only happens when it's raining or any kind of moisture-snow melting on the top of Vehilce. It also happens when I gi through the car wash. So I'm sure it's a moisture problem, but I can't seem to figure it out. Any Ideas? Ford keeps telling me to bring it back every time it happens. I can't afford to dothat! I had them seal the drip pan below the valance on the right fender rearjusty a wiring harness that connects into the fire wall. Please help me, I drive 52 miles a day into work so I need tyo correct this problem soon. Thanks for listening -I'am at my witts end.