1999 Ford Expedition

Engine Performance problem
1999 Ford Expedition V8 Front Wheel Drive Automatic 200000 miles

Just recently, the car has been shaking whenever it's idling or it feel more so when the car is not moving. Anyway, I checked for loose vacuum hoses but could find any that loose or disconnected. I try looking for the spark plugs but could locate them. So, I would appreciate it very much if you could give me a hand in troubleshooting the problem. Thanks - Jim
March 27, 2009.

Jim: I need to know the engine size. If it's the 5.4, the plugs are under the coil packs. Also, has the check engine light come on?