To find them precisely:
1. Consult your owner's manual: This is the best resource. It will have diagrams showing the location of each spark plug and likely details about access.
2. Use a reliable online repair manual: Sites like Chilton or Haynes offer manuals with detailed diagrams and instructions. You'll need to specify the engine size (4.6L or 5.4L) when searching.
3. Look at online forums: Search forums like Expedition forums (search "2004 Expedition spark plug location" + engine size) for images or descriptions from other owners who've done this job. Be aware that information on forums can vary in accuracy.
Important Note: Accessing spark plugs often requires removing parts such as intake manifold components, making it more than just a simple job. Improper access can cause damage. If you're not comfortable with this type of repair, take your vehicle to a qualified mechanic.
