GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2001 🢒 Regal 🢒 Engine 🢒 Engine Mechanical - 3.8L 🢒 Upper Intake Manifold Replacement

Removal Procedure

    Caution: Before servicing any electrical component, the ignition and start switch must be in the OFF or LOCK position and all electrical loads must be OFF, unless instructed otherwise in these procedures. If a tool or equipment could easily come in contact with a live exposed electrical terminal, also disconnect the negative battery cable. Failure to follow these precautions may cause personal injury and/or damage to the vehicle or its components.

  1. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  2. Remove the fuel injector sight shield. Refer to Fuel Injector Sight Shield Replacement .
  3. Disconnect the intake air temperature (IAT) sensor electrical connector.
  4. Remove the air inlet duct from the throttle body.
  5. Drain the cooling system. Refer to Cooling System Draining and Filling in Engine Cooling.
  6. Remove the right spark plug wires from the ignition control module and reposition. Refer to Spark Plug Wire Replacement in Engine Controls - 3.8L.
  7. Relieve the fuel pressure. Refer to Fuel Pressure Relief in Engine Controls - 3.8L.
  8. Remove the fuel rail assembly. Refer to Fuel Injection Fuel Rail Assembly Replacement in Engine Controls - 3.8L.
  9. Remove the brake booster hose from the vacuum source manifold.

    10. Object Number: 190554 Size: SH
  10. Remove the exhaust gas recirculation (EGR) valve wiring harness heat shield nut, bolt and the EGR heat shield.

    11. Object Number: 153567 Size: SH
  11. Remove the throttle body support bracket upper bolt.
  12. Disconnect the electrical connectors from the following:
    13. • EVAP purge solenoid
    • Throttle position (T/P) sensor
    • Idle air control (IAC) valve
    • Manifold absolute pressure (MAP) sensor
    • Mass air flow (MAF) sensor
  13. Remove the EVAP purge solenoid vacuum line from the throttle body.
  14. Remove the accelerator and the cruise control cables with the bracket from the throttle body. Refer to Accelerator Control Cable Bracket Replacement in Engine Controls - 3.8L.

    15. Object Number: 153570 Size: SH
  15. Remove the upper intake manifold bolts and stud.
  16. Clean the upper intake manifold bolt threads.
  17. Remove the upper intake manifold by lifting the back of the intake and sliding the manifold forward from the throttle body support bracket.

    18. Object Number: 405818 Size: SH
  18. Remove the upper-to-lower intake manifold carrier gasket from the upper intake manifold.
  19. If the upper intake manifold is being replaced, remove the following:
    20. • Throttle body
    • Manifold absolute pressure (MAP) sensor
    • Positive crankcase ventilation (PCV) valve
    • Vacuum source manifold

Installation Procedure
  1. If the manifold was replaced install the following:
    2. • Vacuum source manifold
    • Positive crankcase ventilation (PCV) valve
    • Manifold absolute pressure (MAP) sensor
    • Throttle body

    Object Number: 405818 Size: SH
  2. Install the upper-to-lower intake manifold carrier gasket to the upper intake manifold.

    3. Object Number: 153570 Size: SH
  3. Carefully place the upper intake manifold onto the lower intake manifold. Ensure that the alignment pins in the upper intake manifold align with the holes in the lower intake manifold.
  4. Install the upper intake manifold.
  5. Apply thread lock compound GM P/N 12345382 or equivalent, to the bolt threads before assembly.

    6. Object Number: 49828 Size: SH

    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.

  6. Install the upper intake manifold bolts (1-10).

    7. Tighten
    Tighten the upper intake manifold bolts in sequence to 10 N·m (89 lb in).

  7. Install the accelerator and the cruise control cables with the bracket to the throttle body. Refer to Accelerator Control Cable Bracket Replacement in Engine Controls - 3.8L.
  8. Install the EVAP purge solenoid vacuum line to the throttle body.
  9. Connect the electrical connectors to the following:
    10. • Mass air flow (MAF) sensor
    • Manifold absolute pressure (MAP) sensor
    • Idle air control (IAC) valve
    • Throttle position (T/P) sensor
    • EVAP purge solenoid

    Object Number: 153567 Size: SH
  10. Install the throttle body upper support bracket bolt.

    11. Tighten
    Tighten the throttle body support bracket bolts to 10 N·m (89 lb in).


    Object Number: 190554 Size: SH
  11. Install the EGR valve wiring harness heat shield, nut and bolt.

    12. Tighten
    Tighten the EGR valve wiring harness heat shield nut and bolt to 10 N·m (89 lb in).

  12. Install the brake booster hose to the vacuum source manifold.
  13. Install the fuel rail assembly. Refer to Fuel Injection Fuel Rail Assembly Replacement in Engine Controls - 3.8L.
  14. Install the right spark plug wires to the ignition control module. Refer to Spark Plug Wire Replacement in Engine Controls - 3.8L.
  15. Install the air inlet duct to the throttle body.
  16. Connect the intake air temperature (IAT) sensor electrical connector.
  17. Install the fuel injector sight shield. Refer to Fuel Injector Sight Shield Replacement .
  18. Fill the cooling system. Refer to Cooling System Draining and Filling in Engine Cooling.
  19. Connect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  20. Inspect for fluid or vacuum leaks.