Where are spark plugs located on 2003 Ford Expedition?

The spark plugs on a 2003 Ford Expedition are located on the top of the engine, underneath the plastic engine covers. Because there are two different engines commonly found in that model year (a 4.6L V8 and a 5.4L V8), the precise location relative to other engine components will vary slightly. However, they're always accessed from the top. You'll need to remove the plastic engine covers to reach them.