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    Toyota Celica 1986-1993 Repair Guide

    Idle Speed

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    To check idle speed, a tachometer should be connected into the engine electrical system. Having a meter visible under the hood while working is better than running back and forth checking the dashboard tachometer while working.

    Not all tachometers are compatible with the Toyota electrical system. You are cautioned to check with the dealer and/or the tach manufacturer about suitability for your car. After a proper unit is selected, you may have to make or buy an adapter to connect the tachometer test lead to the Toyota terminal. This adapter is quite simple to make and should be kept handy with the tachometer.

    The electrical system and computer(s) are easily damaged or destroyed through careless work habits. Since electricity travels at close to the speed of light, damage is instantaneous and expensive. Always observe these rules when connecting the tachometer:



    Do NOT leave the ignition switch on for more than 5 minutes when the engine is not running.
     
    The tachometer lead must only be connected to the correct terminal; accidental contact with another terminal can cause great damage.
     
    Once connected to the terminal, the tachometer lead and connectors must be protected against grounding to any metal surface of the car. It is highly recommended that any adapter have fully insulated connectors or be wrapped in dry cloth or tape for protection; otherwise, the igniter and/or ignition coil can be damaged.
     
    NEVER disconnect the battery cables while the engine is running.
     
    Make certain the engine and ignition wiring is correctly connected before connecting the tachometer. It is particularly important that ground circuits be clean and tight.
     

    For the 2S-E and 3S-FE engines, the tachometer connector is found at the end of a small wire harness near the distributor. On other models, the tachometer connects to the IG (-) terminal, located in the service connector; this is the same connector needed to check the timing (described earlier). The IG (-) terminal is separate from the other groups of connectors. The tachometer must be connected to this terminal only.

    ADJUSTMENT



    2S-E and 3S-GE Engines


    Click image to see an enlarged view

    Fig. Fig. 1 Connecting a tachometer to adjust idle speed2S-E engine



    Click image to see an enlarged view

    Fig. Fig. 2 Connecting a tachometer to adjust idle speed3S-GE engine

    1. Warm up the engine until it reaches normal operating temperature.
      2.  
    2. The air cleaner should be in place and all wires and vacuum hoses connected. All accessories should be off and the transmission in neutral.
      3.  
    3. Connect a tachometer to the engine.
      4.  



    Click image to see an enlarged view

    Fig. Fig. 3 Pinching vacuum hose No. 13S-GE engine



    Click image to see an enlarged view

    Fig. Fig. 4 Disconnecting the VSV connector2S-E engine



    Click image to see an enlarged view

    Fig. Fig. 5 Adjusting the idle speed2S-E and 3S-GE engines

    1. Run the engine at 2,500 rpm for 2 minutes. This insures that the oxygen sensor and other sensors are fully up to temperature and stabilized.
      2.  
    2. Let the engine return to idle. Pinch the No.1 air intake chamber vacuum hose on the 3S-GE. On the 2S-E, disconnect the Vacuum Switching Valve (VSV) from the Idle Speed Control (ISC) motor.
      3.  
    3. Set the idle speed by turning the idle adjusting screw to obtain the proper idle speed.
      4.  
    4. Remove the tachometer and reinstall any covers or caps which were removed from the service connector.
      5.  

    3S-FE Engine
    1. Make sure all these conditions are met before attempting to adjust the idle: all lines and hoses connected (including vacuum hoses), all fuel injection wiring correctly connected, air cleaner in place, all electrical accessories switched off, transmission in neutral (parking brake set and wheels blocked).
      2.  
    2. Warm the engine to normal operating temperature.
      3.  
    3. Connect the tachometer.
      4.  
    4. Use a jumper wire to connect terminal TE 1 or T and terminal E 1 of the check connector.
      5.  
    5. Hold the engine at 1,000-1,300 rpm for 5 seconds. Release the throttle and check the idle speed. With the jumper wire in place, the idle should be about 650 rpm.
      6.  
    6. If the idle is not at specification, remove the cap and adjust the idle speed adjusting screw on the throttle body.
      7.  
    7. Remove the jumper wire and check the idle speed again; it should now be the value in the Specification Chart.
      8.  
    8. If the idle is not at the specified value, start the engine and idle it for 30 seconds. Turn it off, then repeat the entire pattern (startidleoff) several times. This should store the correct idle value within the Idle Speed Control unit (ISC) and the idle rpm will be at the correct setting.
      9.  
    9. Disconnect the tachometer and replace any covers or plugs which were removed from the service connector.
      10.  



    Click image to see an enlarged view

    Fig. Fig. 6 Shorting the check connector terminals for adjusting the idle speed3S-FE and 1990 5S-FE engines



    Click image to see an enlarged view

    Fig. Fig. 7 Adjusting the idle speed3S-FE and 1990 5S-FE engines

    5S-FE Engine
    1990
    1. Make sure all these conditions are met before attempting to adjust the idle: all lines and hoses connected (including vacuum hoses), all fuel injection wiring correctly connected, air cleaner in place, all electrical accessories switched off, transmission in neutral (parking brake set and wheels blocked).
      2.  
    2. Warm the engine to normal operating temperature.
      3.  
    3. Connect the tachometer.
      4.  
    4. Use a jumper wire to connect terminal TE 1 or T and terminal E 1 of the check connector.
      5.  
    5. Hold the engine at 1,000-1,300 rpm for 5 seconds. Release the throttle and check the idle speed. With the jumper wire in place, the idle should be about 650 rpm.
      6.  
    6. If the idle is not at specification, remove the cap and adjust the idle speed adjusting screw on the throttle body.
      7.  
    7. Remove the jumper wire and check the idle speed again; it should now be the value in the Specification Chart.
      8.  
    8. If the idle is not at the specified value, start the engine and idle it for 30 seconds. Turn it off, then repeat the entire pattern (startidleoff) several times. This should store the correct idle value within the Idle Speed Control unit (ISC) and the idle rpm will be at the correct setting.
      9.  
    9. Disconnect the tachometer and replace any covers or plugs which were removed from the service connector.
      10.  

    1991-93
    1. Make sure the engine is at normal operating temperature. Connect a tachometer and race the engine at 2,500 rpm for 90 seconds. Check the idle speed and compare to the Specifications Chart.
      2.  
    2. If the rpm is not in specification, check the ISC valve.
      1. Connect terminals TE1 and E1 of the check connector with a jumper wire.
        2.  
      2. After the engine rpm are kept at 900-1,300 rpm for 5 seconds, check that idle speed returns.
        3.  
      3. Remove the jumper wire.
        4.  
      4. Disconnect the ISC valve connector.
        5.  
      5. Measure the resistance between the terminal +B and the other terminals (ISCC, ISCO). The resistance should be 19.3-22.3 ohms each.
        6.  
      6. If the resistance is not as specified, remove the ISC valve and gasket from the throttle body and replace them.
        7.  

      3.  
    3. If the idle speed is still not within specifications, check the ECU wiring and ECU system.
      4.  



    Click image to see an enlarged view

    Fig. Fig. 8 Checking the ISC valve resistances1991-93 5S-FE engine

    3S-GTE Engine
    1988-89
    1. Make sure the engine is at normal operating temperature.
      2.  
    2. Disconnect the ISC valve connector.
      3.  
    3. Check that the engine rpm is at 1,000 rpm or more.
      4.  



    Click image to see an enlarged view

    Fig. Fig. 9 Disconnecting the ISC valve connector1988-89 3S-GTE engine



    Click image to see an enlarged view

    Fig. Fig. 1 0Reconnecting the ISC valve connector1988-89 3S-GTE engine



    Click image to see an enlarged view

    Fig. Fig. 1 1Checking the ISC valve resistances1988-89 3S-GTE engine

    1. Reconnect the ISC valve connector.
      2.  
    2. Check that the idle speed returns to 700-800 rpm. If the rpm operation is not as specified, check the ISC valve.
      1. Disconnect the ISC valve connector.
        2.  
      2. Measure the resistance between the terminal +B and the other terminals (ISC 1, ISC 2). The resistance should be 16.0 ohms each.
        3.  
      3. If the resistance is not as specified, remove the ISC valve and gasket from the throttle body, using the proper procedures, and replace.
        4.  

      3.  
    3. If the rpm still are not within specifications, check the ECU wiring and ECU system.
      4.  



    Click image to see an enlarged view

    Fig. Fig. 1 2Removing the ISC valve1988-89 3S-GTE engine



    Click image to see an enlarged view

    Fig. Fig. 1 3Replacing the ISC valve gasket1988-89 3S-GTE engine

    1990-93
    1. Make sure the engine is at normal operating temperature.
      2.  
    2. Disconnect the ISC valve connector.
      3.  
    3. Check that the engine rpm are at 1,000 or more.
      4.  
    4. Reconnect the ISC valve connector.
      5.  
    5. Check that the idle speed returns to 750-850 rpm. If the rpm operation is not as specified, check the ISC valve.
      1. Disconnect the ISC valve connector.
        2.  
      2. Measure the resistance between the terminal +B and the other terminals (RSC, RSO). The resistance should be 19.3-22.3 ohms each.
        3.  
      3. If the resistance is not as specified, remove the ISC valve and gasket from the throttle body and replace them.
        4.  

      6.  
    6. If the rpm still are not within specifications, check the ECU wiring and ECU system.
      7.  



    Click image to see an enlarged view

    Fig. Fig. 1 4Disconnecting the ISC valve connector1990-93 3S-GTE engine



    Click image to see an enlarged view

    Fig. Fig. 1 5Reconnecting the ISC valve connector1990-93 3S-GTE engine



    Click image to see an enlarged view

    Fig. Fig. 1 6Checking the ISC valve resistances1990-93 3S-GTE engine



    Click image to see an enlarged view

    Fig. Fig. 1 7Removing the ISC valve1990-93 3S-GTE engine

    4A-FE Engine
    1. Make sure all these conditions are met before attempting to adjust the idle: all lines and hoses connected (including vacuum hoses), all fuel injection wiring correctly connected, air cleaner in place, all electrical accessories switched off, transmission in neutral (parking brake set and wheels blocked).
      2.  
    2. Warm the engine to normal operating temperature.
      3.  
    3. Connect the tachometer.
      4.  
    4. Hold the engine at 2,500 rpm for approximately 2 minutes.
      5.  
    5. Use a jumper wire to connect terminals Te1 and E1 of the check connector. The idle speed should be 800 rpm with the cooling fan (radiator fan) off.
      6.  
    6. If the idle is not at specification, remove the cap and adjust the idle speed adjusting screw on the throttle body. Make the adjustment with the cooling fan off.
      7.  
    7. Remove the jumper wire and disconnect the tachometer. Replace any caps or covers removed from the service connector.
      8.  



    Click image to see an enlarged view

    Fig. Fig. 1 8Shorting the check connector terminals for adjusting the idle speed4A-FE engine



    Click image to see an enlarged view

    Fig. Fig. 1 9Adjusting the idle speed4A-FE engine

    IDLE MIXTURE ADJUSTMENT



    Idle mixture is controlled completely by the Electronic Control Unit (ECU). Idle mixture is not adjustable on these engines.

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