Ford Expedition

My truck is shaking when running and the service engine soon light is on. It starts just fine, but as soon as it's put into gear it shakes and feels like it's going to turn off. It doesn't but it shakes and this just started two days ago while I was driving on the highway. It's a 2001 Ford Expedition and I just had it winterized and the oil changed today. It has 145,000 miles on it and I have not had one engine problem since I purchased the truck in 2005 used.
November 27, 2007.

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