On a 2001 Ford Escape, the Idle Air Control (IAC) valve is located on the throttle body. The throttle body itself is usually situated at the top of the engine, where the air intake joins the engine. It's a relatively small valve, often cylindrical, and will be connected to both the throttle body and an electrical harness. You'll likely need to look closely to identify it.
To be absolutely certain, you should consult a repair manual specific to your 2001 Ford Escape's engine (it might be a 2.0L or a 3.0L V6). A visual diagram will be extremely helpful in pinpointing its exact location.
