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    2002 GMC Truck Jimmy 2WD (Can) 4.3L SFI 6cyl

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    ISUZU Amigo/Pick-ups/Rodeo/Trooper 1981-1996

    Idle Speed and Mixture Adjustment

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    AIR/FUEL MIXTURE



    1.8L, 2.0L, 2.3L and 2.6L Carbureted Engines

    See Figure 1

    EXCEPT CALIFORNIA ENGINES
    1. Set the parking brake and block the front wheels.
    2.  
    3. Remove the carburetor.
    4.  



    Click image to see an enlarged view

    Fig. Fig. 1: Drill a small hole into the mixture screw cover, then pull it out with a small screw-carbureted engines

    1. Remove the plug for the idle mixture screw. The plug can be removed by drilling a hole and inserting a screw to pull out the plug.
    2.  
    3. Reinstall the carburetor assembly.
    4.  
    5. Connect a tachometer to the engine according to the manufacturer's instructions.
    6.  

    Make the idle speed adjustment with the engine at normal operating temperature.

    1. Make sure that the air cleaner is installed and that the choke valve is open.
    2.  
    3. Disconnect and plug the EGR valve, canister purge line, idle compensator line, and distributor vacuum lines.
    4.  
    5. Adjust the idle speed to 800 rpm.
    6.  
    7. Turn the idle mixture screw all the way in and then back out 3 turns.
    8.  
    9. Adjust the setting of the idle mixture screw to achieve the maximum speed.
    10.  
    11. Reset the throttle screw to 850 rpm.
    12.  
    13. Turn the idle mixture screw clockwise until the engine speed is down to 800 rpm.
    14.  
    15. Insert a new plug for the idle mixture screw.
    16.  
    17. Remove the tachometer and unblock the wheels.
    18.  

    CALIFORNIA ENGINES
    1. Firmly set the parking brake and block the drive wheels.
    2.  
    3. Place the transmission in Neutral.
    4.  
    5. Remove the carburetor assembly.
    6.  
    7. Using a drill, drill a hole through the sealing plug covering the idle mixture screw and pry the plug from the carburetor.
    8.  
    9. Reinstall the carburetor.
    10.  
    11. Connect a tachometer according to the manufacturer's instructions.
    12.  
    13. Operate the engine until it reaches normal operating temperatures. Be sure the choke is fully open and the air cleaner is installed. If equipped, turn the air conditioning OFF.
    14.  
    15. Disconnect and plug the distributor vacuum, the canister purge and EGR vacuum lines. Shut off the vacuum to the idle compensator by bending the rubber hose.
    16.  
    17. Connect a dwell meter (4-cylinder scale) or duty meter to the duty monitor lead.
    18.  
    19. Turn the idle mixture screw all the way in and back out 1 1 / 2 turns.
    20.  
    21. Turn the throttle adjusting screw until the engine speed is 950 rpm (1986-87) or 900 rpm (1988-90). Also refer to the Gasoline Engine Tune-up Specification chart in this section.
    22.  
    23. Adjust the idle mixture screw to achieve an average dwell of 36° or duty of 40 percent.
    24.  

    The dwell or duty reading specified is the average of the most constant variation.

    1. Reset the throttle adjusting screw until the engine speed is 850-950 rpm.
    2.  
    3. Reinstall a mixture adjustment plug.
    4.  
    5. Remove the tachometer and unblock the wheels.
    6.  

    2.2L Gasoline, 2.3L MFI, 2.6L MFI, 2.8L, 3.1L and 3.2L Engines

    The air/fuel mixture is computer controlled according to the needs of the engine and is not adjustable. If the air/fuel mixture is too lean or too rich, other problems with the engine and/or engine control system exist.

    IDLE SPEED



    1.8L, 2.0L, 2.3L and 2.6L Carbureted Engines

    See Figures 2 and 3

    1. Set the parking brake and block the wheels.
    2.  
    3. Place the transmission in neutral.
    4.  
    5. Let the engine warm up to normal operating temperature.
    6.  
    7. Make sure that the choke is fully open and the air cleaner is installed.
    8.  
    9. Connect a tachometer to the engine according to the manufacturer's instructions.
    10.  
    11. Make sure that the air conditioner is OFF.
    12.  
    13. Disconnect and plug the distributor vacuum, the canister purge, and EGR vacuum lines.
    14.  
    15. Shut off the vacuum to the idle compensator by bending the hose.
    16.  



    Click image to see an enlarged view

    Fig. Fig. 2: Carburetor adjusting screws for the 1.8L, 2.0L, 2.3L and 2.6L carbureted engines



    Click image to see an enlarged view

    Fig. Fig. 3: Idle speed adjusting screw (A) location on the carburetor-1.8L, 2.0L, 2.3L and 2.6L engines

    1. Turn the throttle adjusting screw to adjust the idle speed to the specific value shown on the VECI label on the vehicle, or in the Gasoline Engine Tune-up Specification chart, later in this section.
    2.  
    3. If the vehicle is equipped with an air conditioner, turn it ON and set the blower to the highest position.
    4.  
    5. Use the FICD adjusting screw (refer to accompanying illustration) at the tip of the carburetor throttle lever to set the fast idle to the specified value.
    6.  
    7. Remove the tachometer and unblock the wheels.
    8.  

    2.2L Diesel Engine

    See Figures 4, 5 and 6

    IDLE SPEED ADJUSTMENT
    1. Set the parking brake and block the drive wheels.
    2.  
    3. With the transmission in Neutral, start the vehicle and warm to normal operating temperature. Make sure the air conditioner is turned off.
    4.  
    5. Connect a tachometer in accordance with the manufacturer's instructions.
    6.  
    7. The proper idle speed is between 700-800 rpm on manual transmission equipped vehicles, and between 800-900 rpm on automatic transmissions.
    8.  
    9. If the idle speed deviates from the proper range, loosen the idle adjusting screw locknut, and turn the screw in or out until the idle speed is correct. Remove the tachometer and unblock the wheels.
    10.  



    Click image to see an enlarged view

    Fig. Fig. 4: Location of the idle adjustment screw-2.2L diesel engine



    Click image to see an enlarged view

    Fig. Fig. 5: Disconnect the hoses (1 and 2Z) from the Vacuum Switching Valve (VSV), then insert a small piece of tubing between the two hoses to connect them together-2.2L diesel engine



    Click image to see an enlarged view

    Fig. Fig. 6: The location of the fast idle adjusting bolt (3) and nut (4)-2.2L diesel engine

    FAST IDLE SPEED ADJUSTMENT
    1. Start the vehicle and warm to normal operating temperature.
    2.  
    3. Connect a tachometer in accordance with the manufacturer's instructions.
    4.  
    5. Disconnect the hoses from the Vacuum Switching Valve (VSV), then connect a 4mm diameter pipe in position between the hoses.
    6.  
    7. Loosen the adjusting nut, and adjust the fast idle speed to 900-950 rpm.
    8.  
    9. Tighten the adjusting nut, and remove the tachometer.
    10.  

    2.2L Gasoline, 3.1L and 3.2L Engines

    The idle speed is controlled by the Idle Air Control (IAC) motor which, is also controlled by the Powertrain Control Module (PCM) or Electronic Control Module (ECM). Since the PCM/ECM regulates the idle speed under all conditions, the idle speed is not adjustable.

    2.3L MFI, 2.6L MFI and 2.8L Engines
    1988-95 MODELS

    See Figures 7, 8, 9, 10, 11 and 12



    Click image to see an enlarged view

    Fig. Fig. 7: Before adjusting the idle speed, make sure to detach the EGR vacuum hose ...



    Click image to see an enlarged view

    Fig. Fig. 8: ... as well as the pressure regulator VSV connector and the ...



    Click image to see an enlarged view

    Fig. Fig. 9: ... canister purge vacuum hose-2.3L MFI, 2.6L MFI and 2.8L engines



    Click image to see an enlarged view

    Fig. Fig. 10: The idle speed adjusting screw is located on the side of the throttle body-2.3L MFI and 2.6L MFI engines

    1. Apply the parking brake.
    2.  
    3. The idle speed must be adjusted with the engine running under the following conditions;

      Engine at normal operating temperature
       
      Throttle valve closed and the throttle valve switch idle contact on
       
      Front wheels straight ahead. if equipped with power steering
       
      Air conditioner turned off
       
      Manual transmission in NEUTRAL or automatic transmission in PARK or NEUTRAL
       
      Harness connector for pressure regulator VSV unplugged
       
      Canister purge vacuum hose disconnected and plugged
       
      EGR vacuum hose disconnected and plugged
       

    4.  
    5. Connect a tachometer to the engine.
    6.  
    7. If the idle speed does not match the value shown on the VECI label, or in the Gasoline Engine Tune-up Specification chart later in this section, it is incorrect. Turn the adjustment screw on the throttle body to obtain the correct idle speed.
    8.  
    9. Connect the pressure regulator VSV harness connector and disconnect the tachometer from the engine.
    10.  
    11. Connect the vacuum hoses for the EGR and the charcoal canister.
    12.  

    1996 MODELS

    The engine control system determines the idle speed for this engine. If the idle speed is out of specification, it may be a symptom of an engine control system problem. The idle speed cannot be adjusted.

    1. Apply the parking brake.
    2.  
    3. The idle speed must be inspected with the engine running under the following conditions;

      Engine at normal operating temperature
       
      Throttle valve closed and the throttle valve switch idle contact on
       
      Front wheels in the straight ahead position, if equipped with power steering
       
      Air conditioner and all electrical accessories turned OFF
       
      Manual transmission in N or automatic transmission in the P or N position
       

    4.  
    5. Connect a tachometer to the engine.
    6.  
    7. If the idle speed does not match that of the VECI label on the vehicle or the Gasoline Engine Tune-up Specification chart later in this section, it is out of adjustment and the engine control system must be inspected.
    8.  
    9. Disconnect the tachometer from the engine.
    10.  



    Click image to see an enlarged view

    Fig. Fig. 11: GASOLINE ENGINE TUNE-UP SPECIFICATIONS



    Click image to see an enlarged view

    Fig. Fig. 12: DIESEL ENGINE TUNE-UP SPECIFICATIONS

     
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