To find out which cylinder is #4, you'll need to:
1. Identify your engine size: Check your vehicle's paperwork or the engine itself for the displacement (4.6L or 5.4L).
2. Find a diagram: Once you know the engine size, search online for "2005 Ford Expedition [4.6L or 5.4L] engine firing order." A diagram showing the cylinder arrangement and numbering will be available. Many repair manuals or automotive websites (like repair manuals or forums dedicated to Ford Expeditions) will have these diagrams.
The firing order (the sequence in which the cylinders fire) is crucial because the cylinder numbers are assigned based on that order, not on a simple left-to-right arrangement.