There was a time when a car's engine idle speed was controlled mechanically by the slight opening of the carburetor's throttle valve. Ford's 1999 Escort relied on a fuel-injected throttle body that constantly fed the 2.0-liter engine and accommodated for changing road and weather conditions. The idle was dynamically controlled by an idle air control valve attached to the throttle body. A failing IAC valve can cause the Escort to idle roughly and stall, or become difficult to start. Most of these problems will also be accompanied by a check engine light on the dashboard.
Raise the hood and follow the air intake duct from the air filter box on the driver's side of the engine compartment to the throttle body. The IAC valve is the cylindrical component attached to the throttle body with a diamond-shaped flange.
Unplug the IAC valve wiring connector. Remove the two bolts securing the IAC valve to the throttle body, using a ratchet and socket. Pull the IAC valve and gasket away from the engine.
Remove any remaining gasket fragments from the throttle body mating surface with a plastic gasket scraper. Use care to avoid letting any of the fragments fall into the throttle body.
Place the new IAC valve and gasket on the clean throttle body mating surface. Thread both bolts into place by hand, then tighten the bolts to between 71 and 97 inch-pounds with a torque wrench. Plug in the IAC valve connector and lower the hood.
Connect an OBDII-compliant scan tool into the OBDII port under the driver's side dashboard. Follow all directions provided by the tool's manufacturer to clear any trouble codes that may have been stored in your Escort's PCM. Alternatively, take your Escort to a local auto parts store to have the trouble codes cleared.
