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    1970 Buick Electra 7.5L 4BL OHV 8cyl

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    Toyota Camry and Avalon 1997-2000

    Idle Air Control (IAC) Valve

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    OPERATION

    The ECM is programmed with specific engine speed values to respond to different engine conditions (coolant temperature, air conditioner on/off, etc.). Sensors transmit signals to the ECM which controls the flow of air through the bypass of the throttle valve and adjusts the idle speed to the specified value. Some vehicles use an Idle Speed Control (ISC) valve while others use an Air Valve (AV) or Idle Air Control (IAC) valve to control throttle body by-pass air flow.

    TESTING
    5S-FE Engines

    NOTE
    The idle speed must be set correctly before testing the ISC valve.

    1. Bring the engine to normal operating temperature with transmission in N.
    2.  
    3. Using a jumper wire, connect the terminals TE1 and El of the check connector (DLC 1).
    4.  



    Click image to see an enlarged view

    Fig. Attach a jumper wire to the terminals TE1 and E1 in the DLC 1

    1. The engine rpm should rise to 900-1300 rpms for 5 seconds. Check that it returns to idle speed. If rpm is as specified, the valve is functioning properly.
    2.  
    3. If rpm did not function as specified, stop the engine and disconnect the jumper wire.
    4.  
    5. Disengage the ISC valve connector.
    6.  
    7. Using an ohmmeter, measure the resistance between the +B terminal (middle terminal) and the ISC1-ISC2 (3S-FE) and the ISCC-ISCO (5S-FE) outer terminals.
    8.  



    Click image to see an enlarged view

    Fig. Attach an ohmmeter and measure the resistance between the three terminals-3S-FE engine



    Click image to see an enlarged view

    Fig. Attach an ohmmeter and measure the resistance between the three terminals-5S-FE engine

    1. The resistance should be 16-17 ohms on the 3S-FE engine and 19.3-22.3 ohms on the 5S-FE engine.
    2.  
    3. If not as specified, replace the ISC valve.
    4.  

    1MZ-FE Engine

    NOTE
    The idle speed must be set correctly before testing the valve. Make sure the A/C is off during testing.



    Click image to see an enlarged view

    Fig. The IAC valve is attached to the lower portion of the throttle body

    1. Bring the engine to normal operating temperature with transmission in N.
    2.  
    3. Using a jumper wire, connect the terminals TE1 and El of the check connector (DLC 1).
    4.  
    5. The engine rpm should rise to 1000 rpms for 5 seconds. Check that it returns to idle speed. If rpm is as specified, the valve is functioning properly.
    6.  
    7. If rpm did not function as specified, stop the engine and disconnect the jumper wire.
    8.  
    9. Disengage the ISC valve connector.
    10.  
    11. Using an ohmmeter, measure the resistance between the +B terminal (middle terminal) and the RSC and RSO outer terminals.
    12.  



    Click image to see an enlarged view

    Fig. Attach an ohmmeter and measure the resistance between the three terminals-1MZ-FE engine

    1. The resistance should be 21-28.5 ohms on a hot engine.
    2.  
    3. If not as specified, replace the ISC valve.
    4.  

    REMOVAL & INSTALLATION
    1MZ-FE and 5S-FE Engines


    Click image to see an enlarged view

    Fig. Exploded view of the Idle Speed Control (ISC) valve

    1. Remove the throttle body from the vehicle.
    2.  
    3. Remove the four screws that attach the idle speed control (ISC) valve to the throttle body.
    4.  
    5. Lift the ISC valve from the throttle body and remove the gasket.
    6.  



    Click image to see an enlarged view

    Fig. The idle air control valve secured to the bottom of the throttle body with four screws-1MZ-FE engine shown



    Click image to see an enlarged view

    Fig. Be sure to discard the old IAC gasket once the throttle body and valve are separated

    1. Discard the gasket and purchase a new one.
    2.  

    To install:

    1. Place the new gasket onto the throttle body.
    2.  
    3. Install the ISC valve onto the throttle body and install the four screws.
    4.  
    5. Install the throttle body into the vehicle.
    6.  
    7. Inspect the throttle linkage for freedom of movement.
    8.  

     
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