Chevrolet 19333268 Valve Asm,Idle Air Control

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To perform maintenance procedures on the throttle body assembly, start by relieving system fuel pressure and disconnecting the battery's negative terminal. Next, remove the air cleaner housing assembly, adapter, and gaskets. Regarding the Fuel Meter Cover/Fuel Pressure Regulator Assembly, unplug the electrical connectors to the fuel injectors and remove the long and short fuel meter cover screws to take off the fuel meter cover. Remove the fuel meter outlet passage gasket, cover gasket, and pressure regulator seal, and clean the cover if necessary. Install new gaskets and seal, and then reinstall the fuel meter cover assembly using Loctite 262 on the screws. Reattach the electrical connectors to both injectors and the battery cable, checking for leaks with the engine off and the ignition on before reinstalling the air cleaner housing assembly, adapter, and gaskets. For the Fuel Injector Assembly, unplug the electrical connectors from the fuel injectors, remove the fuel meter cover/pressure regulator assembly, and use a screwdriver to carefully pry out the injectors. Remove the upper and lower O-rings and filter from the injector and inspect for dirt and contamination. Replace the injector with an identical part, slide the new filter into place, lubricate and install the new O-rings, and then push the injector into the fuel meter body. Reinstall the fuel meter cover assembly and gasket, the battery cable, and check for fuel leaks. Attach the electrical connectors to the fuel injectors and install the air cleaner housing assembly, adapter, and gaskets. For the Throttle Position Sensor (TPS), remove the TPS and reinstall it on the throttle body, aligning the TPS lever with the TPS drive lever, and secure it with attaching screws and retainers. Reinstall the air cleaner housing assembly, adapter, and gaskets, and attach the battery cable. To remove the Idle Air Control (IAC) valve, unplug its electrical connector and use an adjustable wrench to remove the valve. Remove and discard the old IAC valve gasket, clean the throttle body surface, and check the pintle dimensions. Adjust the pintle if necessary and install the new gasket before reinstalling the IAC valve and securing it to the specified torque. Reconnect the electrical connector and install the air cleaner housing assembly, adapter, and gaskets. For the Fuel Meter Body Assembly, unplug the electrical connectors from the fuel injectors and remove the fuel meter cover/pressure regulator assembly, gaskets, and seals. Remove the fuel injectors, unscrew the fuel inlet and return line threaded fittings, and detach the lines, removing the O-rings. Remove the fuel inlet and outlet nuts and gaskets, then install a new throttle body-to-fuel meter body gasket and place the fuel meter body assembly on the throttle body. Coat the fuel meter body-to-throttle body attaching screws with thread locking compound before tightening them. Install the fuel inlet and outlet nuts with new gaskets, the fuel inlet and return line threaded fittings with new O-rings, and check for leaks. Reinstall the air cleaner housing assembly, adapters, and gaskets. Finally, for the Throttle Body Assembly, unplug all electrical connectors, detach the throttle linkage, return spring(s), transmission control cable (automatics), and cruise control if equipped, and label and detach vacuum hoses. Using a backup wrench, remove the inlet and outlet fuel line nuts and remove the fuel line O-rings, followed by the TBI mounting bolts to lift the TBI unit from the intake manifold, removing and discarding the TBI manifold gasket. Place the TBI unit on a holding fixture if available or be cautious if working directly on a workbench. Remove the fuel meter body-to-throttle body attaching screws, the old throttle body-to-fuel meter body gasket, the TPS, and invert the throttle body to remove the IAC valve. Clean the throttle body assembly, inspect mating surfaces, and reinstall the IAC valve and TPS. Install a new throttle body-to-fuel meter body gasket and place the fuel meter body assembly on the throttle body, securing it with thread locking compound on the attaching screws. Install the TBI unit with a new TBI-to-manifold gasket and new O-rings on the fuel line nuts. Reattach vacuum hoses, throttle linkage, return spring(s), transmission control cable (automatics), cruise control cable, and the grommet with wire harness to the throttle body. Plug in all electrical connectors, connect the negative battery cable, and check for fuel leaks with the engine off and the ignition on. Adjust the minimum idle speed and check the TPS output. Reinstall the air cleaner housing assembly, adapter, and gaskets to complete the maintenance procedures.

The CMFI or CSFI unit precisely controls fuel delivery to the engine, located centrally in the lower intake manifold. Key differences include the CMFI system with an adjustable aluminum air intake plenum and a single non-serviceable fuel injector unit, while the CSFI system has a non-adjustable air intake plenum, six individually controlled fuel injectors, and incorporates a Mass Air Flow sensor. The PCM monitors various engine parameters via sensors and energizes the fuel pump briefly upon ignition. Fuel is supplied by a high-pressure electric pump in the fuel tank, regulated by a fuel pressure regulator. The throttle valve controls air flow, with additional air regulated by the Idle Air Control valve. Fuel is supplied to cylinders through tubes with poppet nozzles. Upper intake manifold removal involves multiple steps, including disconnecting the battery, relieving fuel pressure, removing components, and disconnecting various connectors and hoses. Installation is the reverse of removal. The CMFI and CSFI fuel injection units are removed following a similar process, involving battery disconnection, fuel pressure relief, and removal of related components. Fuel injectors are checked and replaced if needed. The Idle Air Control (IAC) valve controls idle speed and is checked for resistance and operation. Removal and installation steps are provided, including resetting the IAC valve. The intake manifold tuning valve (CMFI) is checked and replaced as needed. Fuel injector replacement (CSFI) includes removing and reinstalling the fuel meter body. The fuel pressure regulator (CSFI) is replaced following specific steps, including O-ring replacement. Throttle body removal and installation (CSFI) involves disconnecting various components and ensuring proper cable operation. Throttle Position Sensor (TPS) checks are detailed, and replacement steps include backprobing, mounting screw removal, and proper alignment during installation.

The throttle body assembly can be replaced without removing it from the intake manifold or fully disassembling it. To begin, relieve the fuel pressure and detach the cable from the negative terminal of the battery. Remove the air cleaner housing assembly, adapter, and gaskets. Next, disassemble the fuel meter cover and fuel injector by removing the injector electrical connector and unscrewing the fuel meter cover retaining screws. Carefully pry the injector from the fuel meter body and remove the fuel meter body if it needs cleaning. Remove the old gasket and clean the fuel meter body thoroughly. Disassemble the fuel injector by removing the small O-ring and fuel filter. The fuel injector cannot be serviced and must be replaced if malfunctioning. To reassemble, install the clean fuel injector nozzle filter and lubricate a new small O-ring before pushing it onto the nozzle end of the injector. Insert the steel backup washer and lubricate a new large O-ring before installing it over the backup washer. Install the injector in the fuel meter body cavity, ensuring it is fully seated. Install new gaskets and a dust seal, then secure the fuel meter cover with thread locking compound. Plug in the electrical connector to the injector and reinstall the air cleaner. For the idle air control (IAC) valve, unplug the electrical connector and remove the valve with a wrench. Measure the distance the valve is extended and adjust it if necessary. Install the new IAC valve with the supplied gasket and plug in the electrical connector. Reinstall the air cleaner and start the engine. Finally, for the throttle position sensor (TPS), unscrew the Torx screws and remove the TPS. Install the new TPS, ensuring the lever is properly engaged with the stop on the throttle body. Reinstall the air cleaner assembly and attach the cable to the negative terminal of the battery. Check for fuel leaks with the ignition switch on and the engine off.

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.