Roadmaster 1992

Throttle Body

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Removal & Installation



At this time the manufacturer does not provide removal and installation procedures for this component. The following procedure is a guideline and may differ from the vehicle you are servicing.


NOTE
Before servicing the vehicle, refer to the Precautions Section.


NOTE
Disconnecting the negative battery cable on some vehicles may interfere with the functions of the on-board computer systems and may require the computer to undergo a relearning process, once the negative battery cable is reconnected.


NOTE
If working near and/or around the SRS system and components, be sure to properly disable the SRS system. See disarming/arming the SRS system.


NOTE
Using the GM diagnostic scan tool or aftermarket equivalent reprogram the necessary systems and components. Be sure to follow the scan tool manufacturer-s directions.

  1. Disconnect the negative battery cable.
  2.  
  3. Properly relieve the fuel system pressure.
  4.  
  5. Remove the air cleaner assembly.
  6.  
  7. Disconnect the electrical connectors at the idle air control, throttle position sensor, and the injector.
  8.  
  9. Disconnect the throttle linkage, return spring, and cruise control (if equipped).
  10.  
  11. Disconnect the throttle body vacuum hoses, fuel supply and fuel return lines.
  12.  
  13. Disconnect the 3 bolts securing the throttle body and remove the throttle body.
  14.  
  15. Discard the gasket. Discard the O-ring.

    Click image to see an enlarged view

    Fig. TBI unit and related components-1991-1993



    Click image to see an enlarged view

    Fig. TBI unit and retaining bolt locations-1991-1993

  16.  

To install:


NOTE
Be sure to use new fasteners, as required.


NOTE
Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread sealer are identified. Do not use paints, lubricants or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners.

  1. Installation is the reverse of the removal procedure.
  2.  

The minimum idle speed should only be adjusted when installing a replacement throttle body. The idle stop screw is used to regulate the minimum idle speed of the engine. On original equipment throttle bodies, it is adjusted at the factory, then covered with a plug to discourage unnecessary readjustment. If necessary to remove the plug, pierce the idle stop screw plug with an awl, and apply leverage to remove it.

The minimum idle speed adjustment is critical to vehicle performance and component durability. Incorrect minimum idle speed adjustment (too high) will cause the IAC valve pintle to constantly bottom out on its seat and result in early valve failure. If the minimum idle speed is adjusted to low, the vehicle may not start in cold weather or may stall during engine warm up.

  1. Block the drive wheels and apply the parking brake. Remove the air cleaner assembly and or air duct. Remove and plug any vacuum hoses on the tube manifold assembly, if equipped.
  2.  
  3. Connect a suitable scan tool onto the ALDL connector. Turn the ignition switch to the ON position.
  4.  
  5. Select the FIELD SERVICE MODE on the scan tool.
  6.  
  7. This will cause the IAC valve pintle to seat in the throttle body (closing the air passage). Wait at least 20 seconds, disconnect the IAC valve connector, then exit the FIELD SERVICE MODE .
  8.  
  9. Using the ROAD TEST MODE on the scan tool, select engine rpm.
  10.  
  11. Place the transmission in the P or N position. Start and run the engine until it reaches normal operating temperature and Closed Loop operation as read on the scan tool. It may be necessary to hold the throttle open slightly to maintain an idle.
  12.  
  13. Select ENGINE RPM on the scan tool and read the engine speed.
    NOTE
    The engine should be at normal operating temperature and in the Closed Loop. Accessories and cooling fan should be off. Vehicles at high altitude may have higher engine rpm.

  14.  
  15. Make sure that the throttle and cruise control cables do not hold the throttle open. The idle speed should be set at the following specifications:
    1. 475 +/- 25 rpm.
    2.  

  16.  
  17. Adjust the minimum idle speed if necessary. Turn the ignition switch to the OFF position.
  18.  
  19. Connect the IAC valve electrical connector.
  20.  
  21. Reset IAC valve pintle position as follows:
    1. Depress accelerator slightly.
    2.  
    3. Start the engine and hold the speed above 2000 rpm for 5 seconds.
    4.  
    5. Turn ignition OFF for 10 seconds.
    6.  
    7. Restart the engine and check for proper idle operation.
    8.  

  22.  
  23. Disconnect the scan tool and remove the blocks from the drive wheels.
  24.  
  25. Install air cleaner assembly.
  26.  
  27. Using the GM diagnostic scan tool or aftermarket equivalent reprogram the necessary systems and components. Be sure to follow the scan tool manufacturer-s directions.
  28.  

 
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