Where is the number three cylinder located on 2003 ford expedition?

On a 2003 Ford Expedition (assuming the 4.6L V8 engine, the most common engine for that year), there isn't a "number three cylinder" in the same way a straight engine would have them numbered consecutively. V8 engines have cylinders arranged in a V-shape.

To understand the cylinder location, you need to visualize the engine layout. The cylinders are usually numbered sequentially starting from one end of the V and proceeding in a specific order (often alternating sides). A mechanic's manual or a detailed engine diagram for a 2003 Ford Expedition 4.6L V8 will show the precise location of each cylinder.

You'll need to consult a repair manual or online resource with a diagram specific to that engine to determine the exact physical location of what would be considered the "3rd" cylinder in the firing order.