Fuel injected engines receive the critical air portion of the fuel/air mixture through the throttle body. The throttle body is typically mounted to the intake plenum downstream of the air filter box. Mechanical linkages, cabling or even an electric motor in throttle-by-wire systems rotate the throttle body blade from the full restricted to the full open to control the amount of airflow into the plenum. Incorrect throttle body operation severely handicaps the engine and may cause it to stall. Cracked, severely corroded or otherwise damaged throttle bodies must be changed to restore engine functionality.
Turn the engine off, open the hood, and allow the engine compartment to cool.
Disconnect the electrical connectors attached to the throttle body. Typical electrical connectors attach to the throttle position sensor, idle air controller, and the idle motor on throttle-by-wire systems. Label the connectors as you disconnect them to make reconnecting easier.
Disconnect the idle air inlet tube. This tube allows a small amount of air to bypass a full closed throttle body blade to give the engine the small amount of air it needs to operate with no pressure applied to the throttle.
Remove the air intake duct leading from the air filter from the throttle body. Top-mounted throttle bodies typically have one long screw with a wing nut and clips holding the duct in place on the throttle body; side or front-mounted setups have clips or screw clamps. Removal of other hardware keeping the duct in place in the engine compartment may be required to adequately move the duct away from the throttle body area.
Disconnect the cables attached to the throttle body. There is typically one for throttle response and one for cruise control. Rotate the throttle body blade open by hand and work the cable ends from their retainers. Fully remove the cable mounting bracket from the throttle body and swing it out of your way with the cables.
Remove all of the bolts holding the throttle body in place. Keep note of each bolt's location, as they may have different lengths or diameters. Lift the throttle body out of the engine compartment and set on a work bench
Remove the various sensors, controllers and other devices mounted to the old throttle body. They are held in place with small screws and usually have their own gaskets. Install them on the new throttle body with new gaskets and make sure they are oriented correctly, not rotated 180-degrees.
Cover the hole in the intake plenum with protective material then clean the throttle body mount location, paying special attention to removing the old gasket. Install the new throttle body gasket on the plenum once it is clean.
Reinstall the throttle body by reversing the removal steps. Attach the mount bolts and throttle cable mount bracket then reconnect the cables, air intake duct, idle air inlet, and electrical connections. When tightening nuts and bolts, be sure to tighten them to the appropriate torque specification.
