GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1999 🢒 Century (China) (CNG) 🢒 Engine 🢒 Engine Mechanical - 3.0L (L46) 🢒 Intake Manifold Installation

Intake Manifold Installation Upper


    Object Number: 371646 Size: SH
  1. Install the upper intake manifold gaskets.
  2. Install the upper intake manifold.

    3. Notice: 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 locking compound or sealant are identified in the service procedure. 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 in order to avoid damage to parts and systems.

  3. Install the upper intake manifold bolts and studs. Apply threadlock GM P/N 12345382 or equivalent to the threads.

    4. Tighten
    Tighten the upper intake manifold bolts and studs to 25 N·m (18 lb ft).


    Object Number: 371637 Size: SH
  4. Install the spark plugs.

    5. Tighten
    Tighten the spark plugs to 27 N·m (20 lb ft).

  5. Install the electronic ignition control module.
  6. Install the electronic ignition control module nuts and bolts.

    7. Tighten
    Tighten the electronic ignition control module nuts and bolts to 25 N·m (18 lb ft).

  7. Install the spark plug wires.

    8. Object Number: 511787 Size: SH
  8. Install the EGR valve pipe and gasket.

    9. Tighten
    Tighten the EGR valve pipe to 25 N·m (18 lb ft).

  9. Install the EGR valve and gasket.
  10. Install the EGR valve bolts.

    11. Tighten
    Tighten the EGR valve bolts to 30 N·m (18 lb ft).

  11. Install the spark plug wires.

    12. Object Number: 475269 Size: SH
  12. Install the MAP sensor bracket.
  13. Install the MAP sensor bracket bolt.

    14. Tighten
    Tighten the MAP sensor bracket bolt to 25 N·m (18 lb ft).


    Object Number: 475271 Size: SH
  14. Install the MAP sensor.
  15. Install the MAP sensor bolts.

    16. Tighten
    Tighten the MAP sensor bolts to 5 N·m (44 lb in).

  16. Install the MAP sensor electrical connector.

Intake Manifold Installation Lower


    Object Number: 843417 Size: SH

    Important: All gasket-mating surfaces need to be free of oil, and foreign material. Use GM P/N 12346139 (Canadian P/N 10953463) or equivalent to clean surfaces.

  1. Install the lower intake manifold gaskets.
  2. With gaskets in place apply a small drop 8-10 mm (0.31-0.39 in) of RTV sealer GM P/N 12346141 (Canadian P/N 10953433) or equivalent to the 4 corners of the intake manifold to block joint (1).
  3. Connect the 2 small drops with a bead of RTV sealer that is between 8-10 mm (0.31-0.39 in) wide and 3.0-5.0 mm (0.12-0.20 in) thick (2).
  4. Install the lower intake manifold.

    5. Object Number: 187067 Size: SH

    Notice: Maximum gasket performance is achieved when using new fasteners, which contain a thread-locking patch. If the fasteners are not replaced, a thread locking chemical must be applied to the fastener threads. Failure to replace the fasteners or apply a thread-locking chemical MAY reduce gasket sealing capability.

    Important: All lower intake manifold bolts need to be cleaned, free of any foreign material, and reused only if new bolts are unavailable. Use GM P/N 12345382 (Canadian P/N 10953489) or equivalent and apply to the old intake manifold bolt threads.

    Important: Manufacturer recommends the center bolts be fully torqued before the diagonal bolts to assure proper seal ability.

    Important: Lower intake manifold bolts in location 6 and 7 should be torqued to specification using a crows foot type tool.

    Notice: 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 locking compound or sealant are identified in the service procedure. 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 in order to avoid damage to parts and systems.

  5. Install the lower intake manifold bolts.

    6. Tighten

    1. Tighten the lower intake manifold center bolts in sequence to 7 N·m (62 lb in) on the first pass.
    2. Tighten the lower intake manifold center bolts in sequence to 13 N·m (115 lb in) on the final pass.
    3. Tighten the lower intake manifold diagonal bolts in sequence to 13 N·m (115 lb in) on the first pass.
    4. Tighten the lower intake manifold diagonal bolt in sequence to 25 N·m (18 lb ft) on the final pass.

    Object Number: 523326 Size: SH
  6. Install the heater inlet pipe.
  7. Install the heater inlet pipe nut.

    8. Tighten
    Tighten the heater inlet pipe nut to 25 N·m (18 lb ft).


    Object Number: 862487 Size: SH

    Important: Do not press on the fuel pressure regulator valve when installing the fuel injector rail assembly.

  8. Install the fuel injector rail assembly.
    9. 8.1. Install the fuel injector O-rings using GM P/N 12345616, (Canadian P/N 993182) or equivalent.
    8.2. Install the injector nozzles into the lower intake manifold injector bores.
    8.3. Press on the injector rail using the palms of both hands until the injectors are fully seated.
  9. Install the fuel injector rail bolts.

    10. Tighten
    Tighten the fuel injector rail bolts to 10 N·m (89 lb in).


    Object Number: 187065 Size: SH
  10. Install the fuel feed and return pipe retaining clip.
  11. Install the fuel feed and return pipe retaining clip bolt.

    12. Tighten
    Tighten the fuel feed and return pipe retaining clip bolt to 8 N·m (71 lb in).