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    Suzuki Samurai/Sidekick/Tracker 1986-1998 Repair Guide

    Idle Speed Control Solenoid (ISCS) Valve

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    Only the 1.3L TFI and 1989-91 1.6L engines are equipped with an Idle Speed Control Solenoid (ISCS) valve.

    OPERATION



    The purpose of the Idle Speed Control Solenoid (ISCS) valve is to control engine idle speeds while preventing stalling due to changes in engine load. The ISCS valve performs four important functions, namely:



    To maintain specified engine idle speed at all times.
     
    To improve engine starting.
     
    To compensate the air/fuel mixture ratio during deceleration (dash-pot effect).
     
    To improve driveability when the engine is at normal operating temperature.
     

    The ISCS valve assembly controls bypass air around the throttle plate. By closing or opening the bypass air passage, a controlled amount of air can move around the throttle plate. If engine speed (rpm) is too low, more air is diverted around the throttle plate to increase engine speed.

    During idle, the proper cycle of the ISCS valve is calculated by the ECM based on engine condition. Engine condition is calculated by the ECM based upon incoming information (such as battery voltage, coolant temperature, engine load, engine speed, etc.) from numerous sensors. If the engine speed drops below a specified rate with the throttle plate closed, the ECM will then alter the frequency of the valve cycle.

    TESTING



    1.3L TFI and 1991 1.6L TFI Engines

    See Figures 1 and 2

    1. Ensure the ignition switch is OFF , then detach the wiring harness connector from the valve.
    2.  
    3. Using a Digital Volt-Ohmmeter (DVOM), switched to the ohmmeter setting, measure the resistance between the two valve terminals. The resistance should be between 30-33 ohms for 1.3L TFI engines, and 11-14 ohms for 1991 1.6L TFI engines at 68°F (20°C). If the value observed is not within this specified range, replace the valve with a new one.
    4.  



    Click image to see an enlarged view

    Fig. Fig. 1: Use a DVOM to measure the resistance of the ISCS valve, and replace the valve if the resistance is not within the specified ranges



    Click image to see an enlarged view

    Fig. Fig. 2: Detach the air cleaner case-to-ISCS valve vacuum hose from the air cleaner, and ensure that no air is being drawn into the hose

    1. Start the engine and allow it to reach normal operating temperature.
    2.  
    3. With the engine idling and the wiring harness still detached from the valve, disconnect the air cleaner housing-to-ISCS valve vacuum hose from the air cleaner housing. Ensure that no air is being drawn in the hose.
    4.  
    5. Connect a 12 volt DC battery to the ISCS valve terminals, then check that air is being drawn into the disconnected end of the air cleaner housing-to-ISCS valve vacuum hose.
    6.  
    7. If the valve did not perform as described, replace it with a new one.
    8.  

    1989-90 1.6L TFI Engines

    1. Ensure the ignition switch is OFF , then detach the wiring harness connector from the valve.
    2.  
    3. Using a Digital Volt-Ohmmeter (DVOM), switched to the ohmmeter setting, measure the resistance between the two valve terminals. The resistance should be between 5.4-6.6 ohms at 68°F (20°C). If the value observed is not within this specified range, replace the valve with a new one.
    4.  



    Click image to see an enlarged view

    Fig. Fig. 3: Use a DVOM to measure the resistance of the ISCS valve-1989-90 1.6L engine shown

    REMOVAL & INSTALLATION



    1.3L TFI and 1991 1.6L TFI Engines
    1. Disconnect the negative battery cable.
    2.  
    3. Detach and label the wiring harness connector and vacuum hoses from the ISCS valve.
    4.  
    5. Loosen the retaining fasteners, then remove the valve from the engine compartment.
    6.  

    To install:
    1. Install the valve in position and tighten the retaining fasteners until snug.
    2.  
    3. Reattach the vacuum hoses and wiring harness connector to the valve. Ensure that the connector retaining latch is fully engaged.
    4.  
    5. Connect the negative battery cable.
    6.  

    1989-90 1.6L TFI Engines

    1. Disconnect the negative battery cable.
    2.  
    3. Detach and label the wiring harness connector from the ISCS valve wiring.
    4.  
    5. Using a thin, metal prytool, such as a scratch awl, disengage the wiring terminals from the TP sensor/ISCS valve plastic connector.
    6.  
    7. Loosen the retaining fasteners, then remove the valve from the throttle body.
    8.  



    Click image to see an enlarged view

    Fig. Fig. 4: To remove the ISCS valve, disengage the wiring harness connector from the valve wiring ...



    Click image to see an enlarged view

    Fig. Fig. 5: ... then separate the two wire terminals from the ISCS valve/TP sensor connector



    Click image to see an enlarged view

    Fig. Fig. 6: Loosen the ISCS valve mounting screws ...



    Click image to see an enlarged view

    Fig. Fig. 7: ... then separate the valve from the throttle body assembly

    To install:
    1. Along with a new gasket, install the valve on the throttle body, then tighten the retaining screws until secure.
    2.  
    3. Insert the wiring terminals in the TP sensor/ISCS valve connector until they are fully engaged. Give both wires a slight tug to ensure that they will not back out of the connector.
    4.  
    5. Reattach the wiring harness connector to the valve wiring. Ensure that the connector retaining latch is fully engaged.
    6.  
    7. Connect the negative battery cable.
    8.  

     
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