A sealant which is applied to the downstream side of the throttle plate and bore area to reduce plate-to-bore leakage. This sealant makes the throttle body tolerant of sludge accumulation and should not be removed or cleaned.
Section 03-04A: Fuel Charging and Controls, 4.9L Engine | 1996 Vehicles Equipped with 4.9L SFI Engines Workshop Manual |
The throttle body (9E926) controls airflow to the engine (6007) through a double butterfly-type valve. The throttle position is controlled by multiple-link, progressive opening throttle linkage. The body is a single-piece die casting made of aluminum. It has a dual bore with an air bypass channel around the throttle plate. This bypass channel controls both cold and warm engine idle control as regulated by an idle air control valve (IAC valve) (9F715) mounted directly to the throttle body. The valve assembly is an electromechanical device controlled by the powertrain control module (PCM) (12A650). It incorporates a linear actuator which positions a variable area metering valve.
Other features of the throttle body include:
A preset stop to locate the wide open throttle (WOT) position.
A throttle body-mounted throttle position sensor (TP sensor) (9B989).
Two canister purge ports for evaporative emission control.
A throttle return center (TRC) screw that sets the closed position of the throttle plate. Do not adjust or tamper with the TRC screw unless instructed to do so by the Powertrain Control/Emissions Diagnosis Manual. If the TRC screw is advanced too far, too much air will be allowed at idle making it impossible for the powertrain control module to properly control idle speed and mixture through the injectors and idle air control valve. If backed-off too much, the throttle plate will stick.
A sealant which is applied to the downstream side of the throttle plate and bore area to reduce plate-to-bore leakage. This sealant makes the throttle body tolerant of sludge accumulation and should not be removed or cleaned.