To find cylinder 5, you need to know the firing order. The firing order varies slightly depending on the specific engine calibration, but a typical firing order for the 5.4L Triton V8 is 1-3-7-2-6-4-8-5.
Therefore, cylinder 5 is located on the passenger side (right side) of the engine, towards the rear (further away from the front of the vehicle). It's essential to consult a repair manual specific to your year and model Expedition for the exact firing order and cylinder location diagrams. These diagrams will clearly show the cylinder positions and make identification much easier.