To be more precise, look for a small, usually cylindrical valve mounted directly on or very near the throttle body. The throttle body itself is located on the intake manifold, usually near the front of the engine. It's a relatively accessible component.
Because pinpointing the *exact* location without the year and engine is impossible, it is recommended you consult a repair manual specific to your Ford Expedition's year and engine. A repair manual (either printed or online) will have diagrams showing the exact location and often photos. You can also search online for "[Your Expedition's Year and Engine] IAC valve location" – images from other owners' repairs often help.
