The throttle position sensor (TPS) in a Quadrajet carburetor is located inside the body of the carburetor. It is actuated by the accelerator pump lever on the top of the carburetor. Replacement requires removal of the top of the carburetor and special tools to adjust the replacement TPS. You don't need to remove the carburetor to change and adjust the TPS. Just be careful not to drop small screws and parts down the throat of the carburetor into the engine.
Remove the wing nut on top of the air cleaner. Lift up on the air cleaner and unplug the two vacuum lines attached to its bottom. Lift the air cleaner out of the engine compartment and lay it aside.
Remove the accelerator pump lever pivot pin by tapping it through the lever using a roll pin punch. Unhook the lever from the linkage and lay it aside. Remove the small screw that attaches the linkage arm to the shaft of the primary butterfly valve on the right side of the carburetor. Lay the linkage arm aside.
Unscrew the air cleaner mounting stud from the top of the Quadrajet. Remove the top of the carburetor using a screwdriver to remove the nine mounting screws. There are seven external mounting screws and two additional mounting screws hidden under the rear butterfly valve.
Lift the top of the carburetor up off the carburetor. Lay the top of the carburetor aside. Slide the old sensor and electrical connector, located in the right front of the carburetor body, out of the carburetor body. Slip the new sensor in place.
Install a new gasket on top of the body of the carburetor. Use a small screwdriver to push the spring-loaded TPS sensor into the carburetor body. Reinstall the top of the carburetor and start the mounting screws by hand. Tighten all of the mounting screws securely.
Reinstall the primary linkage arm. Position the accelerator pump lever into the top of the carburetor and pry the pivot pin into the pump arm using a screwdriver. Screw the air cleaner stud into the top of the carburetor and reinstall the air cleaner.
