To perform various maintenance procedures on the throttle body assembly, first, relieve fuel pressure and disconnect the battery's negative terminal. When working on the fuel injector, unplug its electrical connector, remove the injector retainer screw, and carefully pry it out, replacing upper and lower O-rings after removal. Inspect the fuel injector filter and check for dirt in fuel lines and the tank. Install a new O-ring lubricated with transmission fluid, ensuring proper placement. Push the injector assembly straight into the fuel injector cavity, aligning the electrical connector end. Secure it with a threaded locking compound on the retainer screw. Afterward, reinstall the air cleaner housing assembly, adapter, and gaskets, checking for fuel leaks with the engine off and the ignition on. For the fuel pressure regulator, remove the pressure regulator cover assembly by taking out the four attaching screws while keeping the regulator compressed, and replace the pressure regulator diaphragm assembly if needed. Install the new diaphragm, spring seat, and spring, ensuring the diaphragm is seated properly. Reconnect the cover assembly over the diaphragm, aligning mounting holes, and secure it with four screw assemblies coated with thread locking compound. Reconnect the negative battery cable and check for fuel leaks with the engine off and the ignition on. To maintain the Throttle Position Sensor (TPS), unplug its electrical connector, remove two attaching screws, and reinstall the TPS on the throttle shaft with the throttle valve closed. Rotate it counter-clockwise to align the mounting holes, and then secure it with the two attaching screws. Reinstall the air cleaner housing assembly, adapter, and gaskets, and reattach the cable to the negative battery terminal. For the Idle Air Control (IAC) valve, unplug its electrical connector, remove the IAC valve mounting screws, and then remove the IAC valve. Replace the O-ring and clean the IAC valve seating surfaces. Measure the distance between the valve pintle tip and the flange mounting surface when fully extended; if it exceeds specifications, reduce it to prevent damage. Retract the IAC valve, lubricate a new O-ring with transmission fluid, and install it. Secure the IAC valve to the throttle body with thread locking compound on the attaching screws and plug in its electrical connector. Reinstall the air cleaner housing assembly, adapter, and gaskets, and reconnect the battery cable. Start the engine, allow it to reach operating temperature, and the PCM will set the proper idle speed. For the Tube Module Assembly, remove the tube module assembly attaching screws, discard the old gasket, and clean any residual gasket material from the throttle body. Install a new tube module gasket and the tube module. Reinstall the air cleaner housing assembly, adapter, and gaskets. To maintain the Fuel Meter Assembly, remove the throttle body injection unit and the two fuel meter body attaching screws and washers to remove the fuel meter assembly. If installing a new fuel meter, remove the fuel pressure regulator and fuel outlet nut and transfer them to the new fuel meter. Discard the old fuel meter body-to-throttle body gasket and replace it with a new one. Install the fuel meter onto the throttle body and tighten the attaching screws. For the Throttle Body Assembly, unplug the electrical connectors from the fuel injector, IAC, and TPS. Remove the throttle body mounting studs and the old throttle body-to-intake manifold gasket. Install the new tube module assembly, IAC valve, and TPS on the new throttle body assembly. Install a new fuel meter body-to-throttle body gasket, matching cutouts with openings. Install the fuel meter assembly and fuel injector. Finally, install a new throttle body-to-intake manifold gasket and the throttle body assembly on the intake manifold, tightening the mounting studs to specified torque values. To perform the minimum idle speed adjustment, ground the diagnostic terminal of the ALDL connector, turn on the ignition, wait 30 seconds, unplug the IAC valve electrical connector, start the engine, and adjust the idle stop screw with the transmission in Neutral (manual) or Park (automatic) to obtain the specified RPM. Reconnect the IAC valve electrical connector, unplug any vacuum line ports, and reinstall the air cleaner housing assembly, adapter, and gaskets. For a non-adjustable TPS output check, connect a digital voltmeter from center terminal "8" to outside terminal "A" of the TPS connector. With the ignition on and the engine off, the TPS voltage should be less than 1.25 volts. If the voltage exceeds specifications, replace the TPS.
Posted by GMPartsGiant Specialist