Where is the idle air control located on a 1999 ford expedition?

On a 1999 Ford Expedition, the Idle Air Control (IAC) valve is typically located on the throttle body. The throttle body itself sits on the intake manifold, near the engine's front. It's a relatively small cylindrical component attached to the throttle body, often with a single electrical connector.

However, without visual confirmation, it's impossible to give an exact location. A repair manual specific to your 1999 Ford Expedition's engine (4.6L or 5.4L V8) would be the best resource to pinpoint its precise location with a diagram. You could also search online for images of "1999 Ford Expedition throttle body" to aid in identification.