How to Replace a Lincoln Towncar IAC Valveby Don Bowman
The IAC valve is the idle air control valve for the Lincoln Towncar's fuel injected engine. The throttle valve in the throttle body is completely closed when the throttle is released. The throttle valve would need to be automatically moved to the open and closed position continuously to control the idle. It is much simpler to install an air bypass valve that picks up air in front of the throttle plate. It directs the air through a control device that meters the amount of air and passes it through to the engine side of the throttle plate. The idle air control is an electric motor that operates a pintle. This pintle is a short rod with a cone on the end that opens and closes off the air hole governing the amount of air necessary for proper idle. The IAC makes numerous adjustments every second. It is located right alongside the throttle body.
Pull the air cleaner assembly from its connecting hose on the engine. Use the common screwdriver to pry the plastic prong out of the connector on the IAC assembly. Take care not to break it. Using the 1/4-inch ratchet and a 10mm, 1/4-inch socket, unscrew the two 10mm bolts holding the IAC to the intake manifold. Lift off the IAC valve and the gasket.
Place a new gasket on the manifold. Place the new IAC valve on the manifold and screw the two bolts in and tighten. Do not overtighten the bolts.
Plug in the electrical connector to the IAC valve.
Start the engine and allow it to idle for two minutes. Raise the engine rpm up 2000 for one minute and allow the engine to idle.
Put the car in gear at an idle and allow it to idle in gear for five minutes until the computer sets all the parameters again.