GM S-Series Pick-ups and SUV's 1994-1999 Repair Guide

Intake Manifold

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REMOVAL & INSTALLATION



199497 2.2L Engines

UPPER MANIFOLD

See Figures 1 through 6



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Fig. Fig. 1: View of the upper intake manifold-1994-97 2.2L engines

The 2.2L (VIN 4) engine was introduced in 1994 and utilizes a Multi-Port Fuel Injection (MFI) system. The intake manifold is an assembly of separate components, an upper and a lower manifold.

  1. Properly release the fuel system pressure (if the lower manifold assembly is being removed) and disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner ducts.
  4.  
  5. Disconnect the throttle cable support bracket and cable from the manifold.
  6.  
  7. Remove the MAP sensor and the EGR solenoid valve from the upper intake manifold and engine (if the upper manifold is not being replaced, simply unplug the wiring and hoses).
  8.  
  9. Tag and disengage all wiring and vacuum hoses from the upper intake manifold.
  10.  
  11. Loosen the retainers, then remove the upper intake manifold from the engine and lower manifold assembly.
  12.  



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Fig. Fig. 2: Disconnect the vacuum hoses assembly from the throttle body assembly by unfastening the clips



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Fig. Fig. 3: Remove the upper intake manifold retainers ...



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Fig. Fig. 4: ... then separate the upper manifold from the lower manifold



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Fig. Fig. 5: Remove the injector EGR valve from the lower intake manifold



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Fig. Fig. 6: Use a scraper to clean any gasket material from the upper manifold mating surfaces

To install:
  1. Install the upper intake manifold using a new gasket, then tighten the retainers to 22 ft. lbs. (30 Nm).
  2.  
  3. Attach the wiring connectors and vacuum hoses to the upper intake manifold assembly.
  4.  
  5. Install the MAP sensor and EGR solenoid valve.
  6.  
  7. Install and secure the throttle cable support and cable. Tighten the cable bracket bolts to 18 ft. lbs. (25 Nm).
  8.  
  9. Install the air cleaner ducts.
  10.  
  11. Connect the negative battery cable, then start and run the engine to check for leaks.
  12.  

LOWER MANIFOLD

See Figures 7 through 18

  1. Remove the upper intake manifold.
  2.  
  3. Raise and support the front of the vehicle and remove the passenger side wheel.
  4.  
  5. Remove the brackets that attach the wiring and heater hose to the side of the manifold.
  6.  
  7. Disconnect the fuel lines from the rear of the manifold and from the fuel pressure regulator. On some models, the fuel line connected to the regulator may also be attached to the underside of the manifold by a nut and washer. This nut is accessible through a opening on the passengers side wheel well. Locate and loosen the nut, then slide fuel line from under the washer.
  8.  
  9. If applicable, disconnect the heater hose on the right side of the intake manifold.
  10.  
  11. Remove the EGR inlet pipe, if necessary.
  12.  
  13. Tag and disconnect the spark plug wires from the plugs, then pull the spark plug wires through a opening in the manifold until are all underneath the manifold.
  14.  
  15. If necessary, remove the alternator pencil brace. The brace is accessible through the opening in the passenger side wheel well.
  16.  
  17. On 1997 models, remove the fuel injector retainer bracket and disconnect the fuel pressure regulator from the lower intake manifold.
  18.  
  19. On 1997 models, remove the fuel injectors and disconnect the fuel pressure connection fitting.
  20.  
  21. Remove the lower intake manifold retaining nuts.
  22.  
  23. On some models equipped with A/C, the manifold upper studs may have to be removed because the manifold hits the evaporator case, this does not allow enough clearance for manifold removal. Remove the studs using a Torx socket.
  24.  
  25. Remove the lower intake manifold and gasket.
  26.  



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Fig. Fig. 7: Remove the brackets that attach the wiring . .



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Fig. Fig. 8: ... and heater hose to the side of the manifold



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Fig. Fig. 9: Unplug the vacuum tree hose from underneath the manifold and remove the vacuum tree



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Fig. Fig. 10: Disconnect the right side heater hose at the firewall



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Fig. Fig. 11: Disconnect the heater hose from the water outlet by pressing the tabs and pulling on the pipe



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Fig. Fig. 12: Remove the bracket that attaches the fuel line to the rear of the manifold and disconnect the fuel line from the manifold



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Fig. Fig. 13: Unfasten the lower intake manifold retainers



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Fig. Fig. 14: On some models equipped with A/C, you may have to remove the manifold studs because there is not enough clearance to get the manifold past the evaporator core case



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Fig. Fig. 15: Remove the lower intake manifold from the engine compartment



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Fig. Fig. 16: Remove the intake manifold gasket



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Fig. Fig. 17: Location of the lower intake manifold bolt holes



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Fig. Fig. 18: View of the lower intake manifold and its retainer tightening sequence-1994-97 2.2L engines

To install:
  1. Carefully remove all traces of gasket material from the mating surfaces. If the EGR pipe was removed, check the EGR passage to be sure it is free of excessive carbon deposits and clean, as necessary.
  2.  
  3. Install the lower intake manifold using a new gasket.
  4.  
  5. If removed, install the manifold studs.
  6.  
  7. Install and tighten the retaining nut to 24 ft. lbs. (33 Nm) using the sequence illustrated.
  8.  
  9. On 1997 models, connect the fuel pressure connection fitting and install the injectors.
  10.  
  11. On 1997 models, connect the fuel pressure regulator to the lower intake manifold and install the fuel injector bracket.
  12.  
  13. If removed, install the alternator pencil brace.
  14.  
  15. Feed the spark plug wires back up through the opening in the manifold and connect them to the plugs.
  16.  
  17. If removed, install the EGR inlet pipe.
  18.  
  19. If applicable, connect the heater hose on the right side of the intake manifold.
  20.  
  21. Install the brackets that attach the wiring and heater hose to the side of the manifold.
  22.  
  23. Connect the fuel lines. If the fuel line was attached underneath the manifold, don't forget to place the line in position and tighten the nut until snug.
  24.  
  25. Install the upper intake manifold.
  26.  

1998-99 2.2L Engines

See Figures 19 and 20

  1. Disconnect the negative battery cable and remove the air cleaner resonator.
  2.  
  3. Tag and unplug the three vacuum hoses from the throttle body.
  4.  
  5. Remove the throttle cable support bracket and the throttle body assembly.
  6.  
  7. If necessary, remove the upper fan shroud and disconnect the vacuum brake booster hose.
  8.  
  9. If necessary, unfasten the EGR pipe-to-manifold bolts and the EGR pipe-to-EGR adapter bolt, then remove the EGR pipe.
  10.  
  11. If necessary, remove the EGR adapter.
  12.  
  13. Unplug the electrical connections from the following components:
    1. Idle Air Control (IAC) motor
    2.  
    3. Manifold Absolute Pressure (MAP) sensor
    4.  
    5. Throttle Position (TP) sensor
    6.  
    7. Fuel injector harness connector
    8.  

  14.  
  15. Remove the right fender wheelhouse extension.
  16.  
  17. Remove the retainers from the engine harness bracket, the transmission filler tube (if equipped) and the fuel system evaporator pipe.
  18.  
  19. Disconnect the fuel pipes from the fuel rail.
  20.  
  21. Disconnect the accelerator cable and if equipped, the cruise control cable.
  22.  
  23. Tag and disconnect the spark plug wires from the plugs.
  24.  
  25. Remove the spark plug wire harness retainer from the heater hose pipe and set aside the harness.
  26.  
  27. If necessary, remove the alternator rear brace by accessing the retaining nuts and bolts through the wheelhouse.
  28.  
  29. If equipped, remove the engine wiring harness bracket located at the rear of the cylinder head, by unfastening the bracket-to-valve cover and bracket-to-cylinder head retainers, then slide the bracket off the bolt at the rear of the cylinder head.
  30.  
  31. Unfasten the intake manifold bolts.
  32.  
  33. Remove the fuel rail bracket.
  34.  
  35. Remove the intake manifold and gasket.
  36.  



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Fig. Fig. 19: Typical intake manifold mounting-1998-99 models

To install:
  1. Carefully remove all traces of gasket material from the mating surfaces. Check the EGR passage to be sure it is free of excessive carbon deposits and clean, as necessary.
  2.  
  3. Install the lower intake manifold using a new gasket, then tighten the retaining bolts to 17 ft. lbs. (24 Nm) using the sequence illustrated.
  4.  
  5. If removed, install the engine wiring harness bracket. Tighten the bracket-to-valve cover bolts to 88 inch lbs. (10 Nm) and the bracket-to-cylinder head bolt to 18 ft. lbs. (25 Nm).
  6.  
  7. If removed, install the generator rear brace. Tighten the nuts and bolts to 18 ft. lbs. (25 Nm).
  8.  
  9. Install the spark plug wire harness and retainer and attach the spark plug wires to the plugs.
  10.  
  11. Install the throttle body assembly, if removed and the throttle cable support bracket.
  12.  
  13. Attach the three vacuum lines to the throttle body.
  14.  
  15. Attach the accelerator cable and if equipped, the cruise control cable.
  16.  
  17. Connect the fuel lines.
  18.  
  19. Install and tighten the retainers to the engine harness bracket, the transmission filler tube (if equipped) and the fuel system evaporator pipe.
  20.  
  21. Attach the following electrical connections:
    1. Idle Air Control (IAC) motor
    2.  
    3. Manifold Absolute Pressure (MAP) sensor
    4.  
    5. Throttle Position (TP) sensor
    6.  
    7. Fuel injector harness connector
    8.  

  22.  
  23. If removed, install the wheelhouse extension.
  24.  
  25. If removed, install the EGR adapter and tighten the retainers to 97 inch lbs. (11 Nm).
  26.  
  27. Install the EGR pipe to the EGR adapter and tighten the bolt to 18 ft. lbs. (25 Nm).
  28.  
  29. Install the EGR pipe-to-intake manifold bolts and tighten the bolts to 89 inch lbs. (10 Nm).
  30.  
  31. If removed, install the upper fan shroud and the brake booster hose.
  32.  
  33. Install the air cleaner resonator and connect the negative battery cable.
  34.  
  35. Start the engine and check for leaks.
  36.  



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Fig. Fig. 20: Intake manifold bolt tightening sequence-1998-99 models

1994-95 VIN W 4.3L Engines

See Figures 21 and 22



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Fig. Fig. 21: Intake manifold mounting-1994 4.3L (VIN W) engine; note the bolt/stud usage may vary



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Fig. Fig. 22: Intake manifold torque sequence-4.3L (VIN W) engine


CAUTION
Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

  1. Disconnect the negative battery cable and properly relieve the fuel system pressure.
  2.  
  3. Drain the cooling system.
  4.  
  5. Remove the air cleaner and heat stove tube.
  6.  
  7. Remove the two braces at the rear of the serpentine drive belt tensioner.
  8.  
  9. Disconnect the upper radiator hose.
  10.  
  11. Remove the emissions relays along with the bracket, then disengage the wiring harness from the retaining clips and position aside. Disconnect the ground cable from the intake manifold stud.
  12.  
  13. Remove the power brake vacuum pipe, then disconnect the heater hose pipe at the manifold and fuel lines at the TBI unit.
  14.  
  15. Remove the ignition coil, then disengage the electrical connectors at the sensors on the manifold.
  16.  
  17. Matchmark and remove the distributor from the engine. For details, please refer to the procedure in Engine Performance & Tune-up .
  18.  

For ease of installation, DO NOT crank the engine with the distributor removed.

  1. Tag and disengage the wires and hoses from the TBI unit.
  2.  
  3. Disconnect the EGR hose, then disengage the throttle, TVS and cruise control cables (as equipped).
  4.  
  5. Unfasten the intake manifold retaining studs and/or bolts, then remove the manifold and gaskets.
  6.  

To install:

CAUTION
The EPA warns that prolonged contact with used engine oil may cause a number of skin disorders, including cancer! You should make every effort to minimize you exposure to used engine oil. Protective gloves should be worn when changing the oil. Wash your hands and any other exposed skin areas as soon as possible after exposure to used engine oil. Soap and water, or waterless hand cleaner should be used.

  1. Using a putty knife, carefully clean the gasket mounting surfaces. Be sure to inspect the manifold for warpage and/or cracks; if necessary, replace it.
  2.  
  3. Position the gaskets to the cylinder head with the port blocking plates to the rear, then apply a 3 / 16 in. (5mm) bead of RTV sealant to the front and rear of the engine block at the block-to-manifold mating surface. Extend the bead 1 / 2 in. (13mm) up each cylinder head to seal and retain the gaskets.
  4.  
  5. Install the intake manifold taking care not to disturb the gaskets, then tighten the manifold retainers to 35 ft. lbs. (48 Nm) using the proper torque sequence.
  6.  
  7. Engage the TVS, cruise control and/or throttle cables, as equipped.
  8.  
  9. Connect the EGR hose then engage the wires and hoses at the TBI unit as noted during removal
  10.  
  11. Align and install the distributor assembly.
  12.  
  13. Install the ignition coil, then connect the fuel pipes.
  14.  
  15. Connect the heater hose pipe and the power brake vacuum pipe.
  16.  
  17. Connect the ground cable to the intake manifold stud, then position and secure the wiring harness using the clips.
  18.  
  19. Install the emissions relays along with their bracket, then connect the upper radiator hose.
  20.  
  21. Install the brace at the rear of the drive belt tensioner, then install the air cleaner and heat stove tube.
  22.  
  23. Connect the negative battery cable, then properly refill the engine cooling system.
  24.  
  25. Run the engine and check for leaks.
  26.  

1994-95 VIN W 4.3L Engines
upper intake manifold

See Figures 23 through 29



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Fig. Fig. 23: Exploded view of the intake manifold assembly-4.3L VIN W engine



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Fig. Fig. 24: Matchmark the rotor and distributor-to-engine location. This will aid in installation



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Fig. Fig. 25: Unfasten the intake manifold bolts



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Fig. Fig. 26: Remove the intake manifold from the vehicle



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Fig. Fig. 27: Insert shop towels to prevent dirt from entering open ports and passages



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Fig. Fig. 28: Clean the old gasket from the intake manifold mating surfaces using a gasket scraper or putty knife



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Fig. Fig. 29: Upper intake manifold torque sequence-4.3L VIN W engine


CAUTION
Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

If only the upper intake manifold is being removed, the fuel system pressure does not need to be released. ALWAYS release the pressure before disconnecting any fuel lines.

  1. Remove the plastic cover, then properly relieve the fuel system pressure and disconnect the negative battery cable.
  2.  
  3. Drain the engine cooling system, then remove the air cleaner and air inlet duct.
  4.  
  5. Disengage the wiring harness from the necessary upper intake components including:

    Throttle Position (TP) sensor
     
    Idle Air Control (IAC) motor
     
    Manifold Absolute Pressure (MAP) sensor
     
    Intake Manifold Tuning Valve (IMTV)
     

  6.  
  7. Disengage the throttle linkage from the upper intake manifold, then remove the ignition coil.
  8.  
  9. Disconnect the PCV hose at the rear of the upper intake manifold, then tag and disengage the vacuum hoses from both the front and rear of the upper intake.
  10.  
  11. Remove the upper intake manifold bolts and studs, making sure to note or mark the location of all studs to assure proper installation. Remove the upper intake manifold from the engine.
  12.  
  13. Using a putty knife, carefully clean the gasket mounting surfaces. Be sure to inspect the manifold for warpage and/or cracks; if necessary, replace it.
  14.  

To install:
  1. Position a new upper intake manifold gasket on the engine, making sure the green sealing lines are facing upward.
  2.  
  3. Install the upper intake manifold being careful not to pinch the fuel injector wires between the manifolds.
  4.  
  5. Install the manifold retainers, making sure the studs are properly positioned, then tighten them using the proper sequence to 124 inch lbs. (14 Nm).
  6.  
  7. Connect the PCV hose to the rear of the upper intake manifold and the vacuum hoses to both the front and rear of the manifold assembly.
  8.  
  9. Connect the throttle linkage to the upper intake, then install the ignition coil.
  10.  
  11. Engage the necessary wiring to the upper intake components including the TP sensor, IAC motor, MAP sensor and the IMTV.
  12.  
  13. Install the plastic cover, the air cleaner and air inlet duct.
  14.  
  15. Connect the negative battery cable, then properly refill the engine cooling system.
  16.  

lower intake manifold

See Figure 30

  1. Remove the upper intake manifold.
  2.  
  3. Disengage the distributor wiring and matchmark the distributor, then remove the assembly from the engine.
  4.  
  5. Disconnect the upper radiator hose at the thermostat housing and the heater hose at the lower intake manifold.
  6.  
  7. Disconnect the fuel supply and return lines at the rear of the lower intake manifold.
  8.  
  9. Remove the pencil brace (A/C compressor bracket-to-lower intake manifold).
  10.  
  11. Disengage the wiring harness connectors from the necessary lower intake components including:

    Fuel injector
     
    Exhaust Gas Recirculation (EGR) valve
     
    Engine Coolant Temperature (ECT) sensor
     

  12.  
  13. Remove the lower intake manifold retaining bolts, then remove the manifold from the engine.
  14.  

To install:
  1. Using a putty knife, carefully clean the gasket mounting surfaces. Be sure to inspect the manifold for warpage and/or cracks; if necessary, replace it.
  2.  
  3. Position the gaskets to the cylinder head with the port blocking plates to the rear and the "this side up'' stamps facing upward, then apply a 3 / 16 in. (5mm) bead of RTV sealant to the front and rear of the engine block at the block-to-manifold mating surface. Extend the bead 1 / 2 in. (13mm) up each cylinder head to seal and retain the gaskets.
  4.  
  5. Install the lower intake manifold taking care not to disturb the gaskets, then tighten the manifold retainers to 35 ft. lbs. (48 Nm) using the proper torque sequence.
  6.  
  7. Engage the wiring harness to the lower manifold components, including the injector, EGR valve and ECT sensor.
  8.  
  9. Install the pencil brace to the A/C compressor bracket and the lower intake manifold.
  10.  
  11. Connect the fuel supply and return lines to the rear of the lower intake. Temporarily reconnect the negative battery cable, then pressurize the fuel system (by cycling the ignition without starting the engine) and check for leaks. Disconnect the negative battery cable and continue installation.
  12.  
  13. Connect the heater hose to the lower intake and the upper radiator hose to the thermostat housing.
  14.  
  15. Align the matchmarks and install the distributor assembly, then engage the wiring.
  16.  



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Fig. Fig. 30: Lower intake manifold torque sequence-4.3L VIN W engine

1996-99 4.3L Engines
upper intake manifold

See Figure 31



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Fig. Fig. 31: View of the upper intake manifold and related components-1996-99 4.3L engine


CAUTION
Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

  1. Disconnect the negative battery cable and properly relieve the fuel system pressure.
  2.  
  3. Drain the cooling system.
  4.  
  5. Remove the air intake duct.
  6.  
  7. Tag and unplug any necessary wiring harness connectors and move any necessary brackets to one side.
  8.  
  9. Disconnect the throttle cable and if equipped the cruise control cable, then remove the throttle cable bracket from the upper intake.
  10.  
  11. Disconnect the fuel lines and move the brackets from the rear of the lower intake.
  12.  
  13. Disconnect the brake booster vacuum hose and PCV hose from the upper manifold, then remove the ignition coil and bracket.
  14.  
  15. Remove the purge solenoid and bracket, then unfasten the upper intake manifold bolts and studs. Mark the location of the studs to aid in installation.
  16.  
  17. Remove the upper intake manifold.
  18.  

To install:
  1. Position a new upper intake manifold gasket on the engine, making sure the sealing lines are facing upward.
  2.  

Install two stud type bolts into the lower manifold diagonally opposite each other will help in positioning the upper manifold to the lower manifold.

  1. Install the upper intake manifold being careful not to pinch the fuel injector wires between the manifolds.
  2.  
  3. Install the manifold retainers, making sure the studs are properly positioned, then tighten them to 44 inch lbs. (5 Nm) on the first pass and to 88 inch lbs. (10 Nm) on the final pass.
  4.  
  5. Install the purge solenoid and bracket.
  6.  
  7. Install the ignition coil and bracket, the brake booster vacuum hose and PCV hose.
  8.  
  9. Install the fuel lines and the throttle linkage, cruise control linkage (if equipped) and the throttle cable bracket.
  10.  
  11. Engage the wiring harness connectors and brackets.
  12.  
  13. Install the air cleaner intake duct, then connect the negative battery cable.
  14.  
  15. Start the vehicle and check for leaks.
  16.  

lower intake manifold

See Figure 32

  1. Remove the upper intake manifold.
  2.  
  3. Disengage the distributor wiring and matchmark the distributor, then remove the assembly from the engine.
  4.  
  5. Disconnect the upper radiator hose at the thermostat housing and the heater hose at the lower intake manifold.
  6.  
  7. On automatic transmission equipped vehicles, if necessary, disconnect the transmission dipstick tube.
  8.  
  9. Remove the throttle cable and bracket from the throttle body assembly and set them to one side.
  10.  
  11. Remove the EGR tube, clamp and bolt.
  12.  
  13. Disconnect the fuel pipes from the rear of the manifold
  14.  
  15. Disengage the A/C compressor and bracket and move it to one side.
  16.  
  17. Tag and disengage all necessary electrical connections and brackets that would interfere with manifold removal.
  18.  
  19. If necessary for clearance, remove the alternator bracket bolt located next to the thermostat housing.
  20.  
  21. Remove the PCV valve.
  22.  
  23. Remove the lower intake manifold retaining bolts, then remove the manifold from the engine.
  24.  
  25. Using a putty knife, carefully clean the gasket mounting surfaces. Be sure to inspect the manifold for warpage and/or cracks; if necessary, replace it.
  26.  

To install:
  1. Position the gaskets to the cylinder head with the port blocking plates to the rear and the "this side up'' stamps facing upward, then apply a 3 / 16 in. (5mm) bead of RTV sealant to the front and rear of the engine block at the block-to-manifold mating surface. Extend the bead 1 / 2 in. (13mm) up each cylinder head to seal and retain the gaskets.
  2.  
  3. Install the lower intake manifold taking care not to disturb the gaskets, then tighten the manifold retainers in three steps following the sequence shown in the accompanying illustration as follows.
    1. First pass tighten to 26 inch lbs. (3 Nm)
    2.  
    3. Second pass tighten to 106 inch lbs. (12 Nm)
    4.  
    5. Final pass tighten to 11 ft. lbs. (15 Nm)
    6.  

  4.  
  5. If removed, fasten the alternator bracket bolt located next to the thermostat housing.
  6.  
  7. Install the EGR tube, clamp and bolt.
  8.  
  9. Attach all the electrical connectors that were unplugged and install all brackets that were removed to allow access for manifold removal.
  10.  
  11. Attach the fuel lines.
  12.  
  13. Install the A/C compressor and bracket.
  14.  
  15. If removed, install the automatic transmission dipstick tube.
  16.  
  17. Install the throttle linkage and bracket.
  18.  
  19. Connect the heater hose to the lower intake and the upper radiator hose to the thermostat housing.
  20.  
  21. Align the matchmarks and install the distributor assembly, then attach the wiring.
  22.  
  23. Install the vacuum hoses.
  24.  
  25. Install the upper intake manifold.
  26.  



Click image to see an enlarged view

Fig. Fig. 32: View of the lower intake manifold bolt tightening sequence-1996-99 4.3L engine

 
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