Do I need to break into the A/C lines of a 1994 GMC Safari with rear air, when I replace the lower intake manifold gasket? The engine is a 4.3 EFI with throttle body injection.

Check the fuel pressure. It will tell you if the pump, fuel filter, and fuel pressure regulator are all good. Fuel pressure is critical on fuel injected engines.

Check your spark plugs for wear or the wrong gap.

Another possibility is a vacuum or air leak. Check all vacuum hoses and the intake manifold gasket. The GM 3.8L engine is prone to lower intake manifold gasket failures. Sometimes the upper intake gasket, too.

you have a plugged radiator or heater line to back heater unit not allowing coolant to flow

check the vacuum line behind the alternator. the line goes from the intake manifold to the climate control panel. it runs behind the alternator and up to the firewall.the plastic gets brittle and breaks somewhere behind the alternator due to the heat from the engine.

Exactly what is the wrong? Need the part? Need to know torque adjust or porcedure to take off?

For 1994 Pontiac Grand Am 3.1L SFI OHV 6cyl check this procedure for Intake Manifold...
(see Figure 14)
The 3.1L engine is equipped with upper and lower intake manifolds. The upper intake manifold is also known as the intake manifold plenum.

CAUTION The fuel system is under pressure and must be properly relieved before disconnecting the fuel lines. Failure to properly relieve the fuel system pressure can lead to personal injury and component damage.

1. Relieve the fuel system pressure.
2. Disconnect the negative battery cable.
3. Remove top half of the air cleaner assembly and throttle body duct.
4. Drain and recycle the engine coolant.
5. Disconnect the EGR pipe from exhaust manifold.
6. Remove the serpentine belt.
7. Remove the brake vacuum pipe at the intake plenum.
8. Disconnect the control cables from the throttle body and intake plenum mounting bracket.
9. Remove the power steering lines at the alternator bracket.
10. Remove the alternator.
11. Label and disconnect the ignition wires from the spark plugs and wire retainers on the intake plenum.
    
12. Remove the ignition assembly and the EVAP canister purge solenoid together.

Fig. 14: View of the intake manifold and related components

1. Disconnect the upper engine wiring harness connectors at the following components:
   Throttle Position Sensor (TPS) Idle Air Control (IAC) Fuel Injectors Coolant temperature sensor Manifold Absolute Pressure (MAP) sensor Camshaft Position (CMP) sensor
2. Tag and disconnect the vacuum lines from the following components:
   Vacuum modulator Fuel pressure regulator PCV valve
3. Disconnect the MAP sensor from upper intake manifold.
4. Remove the upper intake plenum mounting bolts and lift off the plenum.
5. Disconnect the fuel lines from the fuel rail and bracket.
6. Install engine support fixture special tool J 28467-A or an equivalent.
7. Remove the right side engine mount.
8. Remove the power steering mounting bolts and support the pump out of the way without disconnecting the power steering lines.
9. Disconnect the coolant inlet pipe from the outlet housing.
10. Remove the coolant bypass hose from the water pump and the cylinder head.
11. Disconnect the upper radiator hose at thermostat housing.
12. Remove the thermostat housing.
13. Remove both rocker arm covers.
14. Remove the lower intake manifold bolts. Make sure the washers on the four center bolts are installed in their original locations.
    

When removing the valve train components they should be kept in order for installation the original locations.

1. Remove the rocker arm retaining nuts or bolts and extract the rocker arms and pushrods.
2. Remove the intake manifold from the engine. Remove and discard the gasket.
3. Using a suitable scraper, clean gasket material from all mating surfaces. Remove all excess RTV sealant from front and rear ridges of cylinder block
   

To install:

1. Place a 0.12 inch (3mm) bead of RTV, on each ridge, where the front and rear of the intake manifold contact the block.
2. Using a new gasket, place the intake manifold on the engine.
3. Install the pushrods in their original locations. Coat the pushrods with prelube.

The intake pushrods are marked yellow (5 3 /4 inch long) and the exhaust are green (6 inches long). Make sure the pushrods are properly seated in the valve lifters and rocker arms.

1. Position the rocker arms in there original locations and tighten to specifications. Refer to the procedure earlier in this section.
2. Install lower the intake manifold attaching bolts. Apply sealant 12345739 (or equivalent thread locking compound) to the threads of bolts. Tighten the vertical bolts first then the diagonal bolts to 115 inch lbs. (13 Nm).
3. Install the front rocker arm cover.
4. Install the thermostat housing.
5. Connect the upper radiator hose to the thermostat housing.
6. Fasten the coolant inlet pipe to thermostat housing.
7. Connect coolant bypass pipe at the water pump and cylinder head.
8. Install the power steering pump in the mounting bracket.
9. Loosely install the serpentine belt.
10. Connect the right side engine mount.
11. Remove the special engine support tool.
12. Fasten the fuel lines to fuel rail and bracket.
13. Install the upper intake manifold and tighten the mounting bolts to 18 ft. lbs. (25 Nm).
14. Install the MAP sensor.
15. Connect the upper engine wiring harness connectors to the related components removed earlier.
16. Connect the vacuum lines to the PCV, vacuum modulator and fuel pressure regulator.
17. Install the EVAP canister purge solenoid and ignition assembly.
18. Install the alternator assembly.
19. Connect the power steering line to the alternator bracket.
20. Install the serpentine belt.
21. Connect the spark plug wires to the spark plugs and intake plenum wire retainer.
22. Install the EGR pipe to the exhaust manifold.
23. Attach the control cables to the throttle body lever and upper intake plenum mounting bracket.
24. Install air intake assembly and top half of the air cleaner assembly.
25. Install the brake vacuum pipe.
26. Fill the cooling system.
27. Connect the negative battery cable, then start the vehicle and verify that there are no leaks.

For PARTS REPLACEMENT check in THIS LINK: carpartswholesale.com

Hope helps.

Hello,

Here is a detailed summary on the procedure of how to replace the intake manifold gasket on a 1996 gmc jimmy;
REMOVING THE UPPER INTAKE MANIFOLD(PLENUM)
STEP 1 Disconnect Battery (may not be absolutely necessary, but a good practice to avoid shorting a positive wire to ground).


STEP 2 Remove serpentine belt.

STEP 3 Drain the coolant.

STEP 4 Remove air cleaner ducting and disconnect wires.

STEP 5 Disconnect throttle linkage and bracket.

STEP 6 Disconnect cruise control cable.

STEP 7 Remove brake booster vacuum hose at manifold.

STEP 8 Remove PCV hose.

STEP 9 Remove ignition coil and bracket.

STEP 1O Remove purge solenoid and bracket.

STEP 11 Relieve fuel pressure at test port.

STEP 12 Remove fuel lines and bracket.

STEP 13 Remove upper intake manifold.

REMOVING THE LOWER INTAKE MANIFOLD
STEP 1 Remove the distributor and label the spark plug wires.

STEP 2 Remove heater hoses and bypass hose.

STEP 3 Remove upper radiator hose.


STEP 4 Remove EGR valve?

STEP 5 Remove sensors and bracket on right side.

STEP 6 Remove EGR tube, clamp and bolt.

STEP 7 Remove PCV valve (and replace).

STEP 8 Unbolt A/C compressor and move it aside.

STEP 9 Loosen compressor bracket and slide forward, but do not remove it.

STEP 10 Remove alternator bracket bolt (or remove alternator and set aside)

STEP 11 Unplug all vacuum lines from intake manifold.


STEP 12 Unplug all electrical connectors from manifold.

STEP 13 Take note of the intake manifold bolts and mark the location of the bolts.


STEP 14 Remove intake manifold bolts, and manifold.

STEP 15 Clean mating surfaces

THE MAIN INSTALLATION
STEP1 Set the new gaskets in place and apply silicone to flat areas on front and rear of engine block.

STEP2 Apply thread locking compound to manifold bolts.

STEP 3 Install the manifold and tighten bolts to 35 ft-lbs, in proper sequence.

STEP4 Install the distributor.

STEP5 Install the upper intake manifold.



The remaining installation procedures are basically the reverse of removal.


Have a nice day.

Ha, you tried to fool me with the bit about a 3.5 L motor--I could find that one...here is the complete procedure from AutoZone.com:




Installation To install:

1. Clean the gasket mounting surfaces. Be sure to inspect the manifold for warpage and/or cracks. If necessary, replace it.
2. Position the gaskets on 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 on 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.
   
   Fig. Lower intake manifold tightening sequence-4.3L engines
   
3. Install the lower intake manifold. Tighten the bolts in sequence and in 3 steps, as follows:
   
   
   
   1. Step 1: 26 inch lbs. (3 Nm).
   2. Step 2: 106 inch lbs. (12 Nm).
   3. Step 3: 133 inch. lbs. (15 Nm).
   
   
4. Install or connect the following:
   
   Power steering pump Alternator bracket bolt near the thermostat housing Wiring harness to the lower manifold components, including the injector, EGR valve and ECT sensor Air conditioning compressor bracket-to-the lower intake manifold pencil braces
   
5. Install transmission oil dipstick tube, if necessary.
   
   Fuel supply and return lines to the rear of the lower intake
   
6. Temporarily reattach the negative battery cable, then pressurize the fuel system (by cycling the ignition without starting the engine) and check for leaks.
7. Disconnect the negative battery cable.
8. Install or connect the following:
   
   Heater hose to the lower intake Upper radiator hose to the thermostat housing Distributor assembly and engage the wiring Ignition coil Connect vacuum hoses to the upper and lower intake manifold. New upper intake manifold gasket, making sure the green sealing lines are facing upward Upper intake manifold Manifold retainers. Tighten them to 88 inch lbs. (10 Nm) using two passes. Purge solenoid and bracket Brake booster vacuum hose at the upper intake manifold PCV hose to the rear of the upper intake manifold Vacuum hoses to both the front and rear of the manifold assembly Throttle body Throttle linkage to the upper intake Wiring to the upper intake components including the TP sensor, IAC motor, MAP sensor and the fuel meter Engine cover Air intake assembly
   
9. Connect negative battery cable.
10. Refill the engine cooling system.
11. Start the engine and check for leaks.

3.8L Engine (most common) Upper Intake Manifold To Remove:

1. Drain the cooling system.
2. Remove or disconnect the following:
   • Negative battery cable.
   • Fuel injector sight shield.
   • Air cleaner intake duct.
   • Right spark plug wires from the ignition control module and reposition.
3. Relieve the fuel pressure.
4. Remove or disconnect the following:
   • Fuel rail assembly.
   • Brake booster hose from the vacuum source manifold in the upper intake manifold.
   • Exhaust Gas Recirculation Valve (EGR) wiring harness heat shield nut, bolt and the EGR heat shield.
   • Throttle body support bracket upper bolt.
5. Disconnect the electrical connectors from the following:
   • EVAP purge solenoid
   • Throttle Position (T/P) sensor
   • Idle Air Control (IAC) valve
   • Manifold Absolute Pressure (MAP) sensor
   • Mass Air Flow (MAF) sensor
   • EVAP purge solenoid vacuum line from the throttle body.
   • Accelerator and the cruise control cables with the bracket from the throttle body.
6. Remove or disconnect the following:
   • Upper intake manifold bolts and stud.
   • Clean the upper intake manifold bolt threads.
7. Remove or disconnect the following:
   • Upper intake manifold by lifting the back of the intake and sliding the manifold forward from the throttle body support bracket.
   • Upper-to-lower intake manifold carrier gasket from the upper intake manifold.
8. If the upper intake manifold is being replaced, remove the following:
   • Throttle body assembly.
   • Manifold Absolute Pressure (MAP) sensor.
   • Positive Crankcase Ventilation (PCV) valve.
   • Vacuum source manifold.

Upper intake manifold bolt torque sequence (3.8L engine)

To Install:

1. If the manifold was replaced, install or connect the following:
   • Vacuum source manifold.
   • Positive Crankcase Ventilation (PCV) valve.
   • Manifold Absolute Pressure (MAP) sensor.
   • Throttle body assembly.
   • Upper-to-lower intake manifold carrier gasket to the upper intake manifold.
2. 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. NOTE: Apply thread lock compound, to the bolt threads before assembly.
   
3. Install or connect the following:
   • Upper intake manifold. Tighten the upper intake manifold bolts in sequence to 89 in lbs (10 Nm)
   • Accelerator and the cruise control cables with the bracket to the throttle body.
   • EVAP purge solenoid vacuum line to the throttle body.
4. Connect the electrical connectors to the following:
   • Mass Air Flow (MAF) sensor
   • Manifold Absolute Pressure (MAP) sensor
   • Idle Air Control (IAC) valve
   • Throttle Position (T/P) sensor
   • EVAP purge solenoid
5. Install or connect the following:
   • Throttle body upper support bracket bolt. Tighten the bolt to 89 in lbs (10 Nm)
   • EGR valve wiring harness heat shield, nut and the bolt. Tighten the nut and the bolt to 89 in lbs (10 Nm)
   • Brake booster hose to the vacuum source manifold.
   • Fuel rail assembly.
   • Right spark plug wires.
   • Air cleaner intake duct.
   • Fuel injector sight shield.
6. Connect the negative battery cable.
7. Fill the cooling system.
8. Inspect for fluid or vacuum leaks.

Lower Intake Manifold (W/O Supercharger) To Remove:

1. Remove or disconnect the following:
   • Upper intake manifold.
   • Generator brace.
   • Drive belt tensioner with the mounting bracket and the heater water bypass inlet pipe.
   • Exhaust gas recirculation EGR outlet pipe bolt from the lower intake manifold.
   • Radiator inlet hose from the water outlet housing.
   • ECT sensor electrical connector.
   • Right upper engine mount strut bracket.
   • Generator brace bracket bolts.
   • Generator brace bracket.
   • Lower intake manifold bolts.
   • Lower intake manifold.
   • Lower intake manifold seals.
   • Lower intake manifold gaskets.
2. If replacing the lower intake manifold, Remove or disconnect:
   • Water outlet housing bolt and stud
   • Water outlet housing
   • Gasket and the thermostat.
   • ECT sensor.
3. Inspect the flatness of inlet flanges.
4. Clean the intake manifold mating surfaces.
5. Clean the intake manifold bolts and bolt holes of adhesive compound.

To Install:

1. If removed, install the ECT sensor.
   • Tighten the ECT sensor to 18 ft. lbs. (25 Nm)
2. If removed, install the thermostat, the gasket, and the water outlet housing.
3. If removed, install the water outlet housing bolt and the stud.
   • Tighten the bolt and stud to 20 ft. lbs. (27 Nm)
4. Install or connect the following:
   • Lower intake manifold gaskets. NOTE: Apply sealer GM P/N 12346286 (Canadian P/N 10953472) or equivalent to the ends of the intake manifold seals.
     
   • Lower intake manifold seals.
   • Lower intake manifold.
   • Lower intake manifold bolts.
   NOTE: Apply thread lock compound GM P/N 12345382 (Canadian P/N 10953489) or equivalent to the two hidden bolts and ensure they are installed.
   
5. Tighten the lower intake manifold bolts in sequence to 11 ft. lbs. (15 Nm)
   
   
6. Install or connect the following:
   • Generator brace bracket.
   • Generator brace bracket bolts. Tighten the bolts to 37 ft. lbs. (50 Nm)
   • Right upper engine mount strut bracket.
   • ECT sensor electrical connector.
   • Radiator inlet hose to the water outlet housing.
   • EGR outlet pipe to the lower intake manifold.
   • EGR outlet pipe bolt to the lower intake manifold. Tighten the bolt to 21 ft. lbs. (29 Nm)
   • Drive belt tensioner.
   • Generator brace.
   • Upper intake manifold.
7. Inspect for leaks.

Lower Intake Manifold (W/ Supercharger) To Remove:

1. Disconnect the negative battery cable.
2. Drain the cooling system.
3. Remove the supercharger.
4. Remove the thermostat housing.
5. Remove the EGR pipe at the intake manifold.
6. Disconnect the electrical connection at the temperature sensor.
7. Remove the intake manifold and gaskets.

NOTE: The coolant bypass tube will release from the intake manifold when the manifold is removed.
To Install:

1. Clean the gasket sealing surfaces.
2. Install the intake manifold gaskets.
3. Align the coolant bypass tube with the opening in the intake manifold and install the manifold. Tighten the bolts to 11 lb ft (15 Nm).
4. Install the electrical connector to the temperature sensor.
5. Install the EGR pipe to the intake manifold.
6. Install the thermostat housing.
7. Install the supercharger.
8. Fill the cooling system.
9. Connect the negative battery cable.

It is not necessary to remove the ac lines for removal of the intake manifold.Remove the bolts that hold the ac compressor and it will allow enough room to access the intake.Make sure you mark the location of the number one cylinder on the distributor before removal.

Note, removing the upper intake manifold is not necessary when removing lower intake manifold, they are removed as an assembly.
Disconnect negative battery cable. Drain cooling system. Remove air cleaner assembly and inlet duct. Mark and remove distributor. Remove upper radiator hose at thermostat housing. Disconnect accelerator and cruise control cables. Remove heater hoses from intake manifold. Remove EGR pipe.
Disconnect fuel lines at rear of engine. Remove AC compressor and set aside(leave hoses connected). Remove canister purge solenoid. Disconnect theSCPI injector, ignition coil, Ignition Control Module, generator,IAC motor, TP sensor, O2 sensor, Exhaust Gas Recirculation valve and Engine Coolant Temperature sensor wiring harness connectors. Remove PCV valve and hose. Remove lower intake manifold bolts. Remove lower intake manifold.
Installation.
Always use New O-rings when reconnecting fuel lines at rear of engine. Apply a bead of RTV silicone sealer along the front and rear sealing surfaces of the block.See Fig.6. Install new gaskets and intake manifold on block while RTV is still wet to the touch. Use Threadlock 12345382 or equivalent to lower intake manifold bolts. Tighten lower intake manifold bolts in sequence to specification table. See fig. 7. To complete installation, reverse removal procedure.

3.8L Engine

NOTE The 3.8L (VIN K) non-supercharged engine uses a two-piece intake manifold consisting of an upper air plenum which mounts the throttle body and a lower intake manifold assembly which houses the fuel injectors. The 3.8L (VIN 1) supercharged engine uses a similar lower intake manifold. The supercharger serves as the upper manifold.
Lower Manifold

NOTE Two bolts which fasten the lower intake manifold to the cylinder head are accessible only after the upper intake manifold is removed. These bolts are located in the right front and left rear corners of the lower intake manifold. Remove the upper intake manifold to service the lower intake.
The 3.8L (VIN 1) supercharged engine uses a manifold similar to the 3.8L (VIN K), but the supercharger serves as the upper manifold.

1. Disconnect the negative battery cable.
2. On 3.8L (VIN 1) engines, remove the supercharger assembly. Please see the procedure in this section.
3. Remove the upper intake manifold using the procedure above.
4. Remove the EGR outlet pipe from the intake manifold.
5. Detach the engine coolant temperature sensor wiring harness from the sensor.
6. Remove the lower intake manifold bolts and carefully lift off the manifold.

To install:


Fig. Lower intake manifold bolt torque sequence-3.8L (VIN K) engine

1. Clean all parts well with degreaser, especially the gasket seal surfaces on the upper and lower manifold pieces and between the lower manifold and the cylinder heads..
2. Install new gaskets to the cylinder heads and new seals to the engine block. Carefully lower the manifold into place. Apply thread-locking compound to the bolt threads. Make sure to install the two hidden bolts in the lower intake manifold. Hand start all bolts, then torque evenly to 11 ft. lbs. (15 Nm). Follow the toque sequence, starting in the center, then working outwards in a circle.
3. Install the remaining components in the reverse order of the removal process.

Upper Intake Manifold (Plenum)

1. Disconnect the negative battery cable.
2. On 3.8L (VIN 1) engines, remove the supercharger assembly. Please see the procedure in this section.
3. Tag for identification, then remove the right side spark plug wires.
4. Disconnect the ignition wires from the fuel rail.
5. Remove the fuel rail. Please see Section 5.
6. Remove the cable bracket from the intake manifold.
7. Remove the throttle body.

NOTE Two bolts which fasten the lower intake manifold to the cylinder head are accessible are accessible only after the upper intake manifold is removed. These bolts are located in the right front and left rear corners of the lower intake manifold.

1. Remove the upper intake manifold bolts and carefully lift the upper intake manifold from the engine.

Fig. Upper intake manifold and bolt torque sequence-3.8L (VIN K) engine
To install:

1. Clean all parts well with degreaser, especially the gasket seal surfaces on the upper and lower manifold pieces.
2. Install new gaskets to the cylinder heads and new seals to the engine block. Carefully lower the manifold into place. Make sure to install the two hidden bolts in the lower intake manifold. Hand start all bolts, then torque evenly to 89 inch lbs. (10 Nm). Follow the torque sequence, starting in the center, then working outwards in a circle.
3. Install the remaining components in the reverse order of the removal process.