Lexus GS, SC 1998-06

Spark Plugs

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Inspection




NOTE
Do not use a wire brush for cleaning. Do not attempt to adjust the electrode gap of a used spark plug.

  1. Check the electrode using a megohmmeter to measure the insulation resistance. The resistance should read 10 M- or more.

    Click image to see an enlarged view

    Fig. Using a megohmmeter to measure the insulation resistance.

  2.  
  3. If a megohmmeter is not available, perform the following simple inspection instead:


    1. Quickly accelerate the engine to 4,000 rpm 5 times.
    2.  
    3. Remove the spark plug.
    4.  
    5. Visually check the spark plug. If the electrode is dry, the spark plug is functioning properly. If the electrode is damp, proceed to the next step.

      Click image to see an enlarged view

      Fig. Inspect the condition of the spark plug

    6.  
    7. Check the spark plug for any damage to its threads and insulator. If there is any damage, replace the spark plug. If not, reinstall the spark plug.
    8.  

  4.  
  5. Check the spark plug electrode gap. Maximum electrode gap for a used spark plug should measure 0.047-0.051 inch (1.2-1.3mm). If the gap is greater than the maximum, replace the spark plug. Electrode gap for a new spark plug is 0.039-0.043 inch (1.0-1.1mm).
    NOTE
    If adjusting the gap of a new spark plug, bend only the base of the ground electrode. Do not touch the tip. Never attempt to adjust the gap of a used plug.



    Click image to see an enlarged view

    Fig. Check the spark plug electrode gap.

  6.  

Removal & Installation



  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Disconnect the negative battery cable. Wait at least 90 seconds before performing any other work.
  4.  
  5. Remove the ignition coil(s).
  6.  
  7. Remove the spark plug(s).
  8.  

To install:

  1. Install the spark plug(s). Torque the spark plugs to 13 ft. lbs. (19 Nm).
  2.  
  3. Install the ignition coil(s).
  4.  
  5. Connect the negative battery cable.
  6.  

  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Disconnect the negative battery cable. Wait at least 90 seconds before performing any other work.
  4.  
  5. Remove the ignition coil(s).
  6.  
  7. Remove the spark plug(s).
  8.  

To install:

  1. Install the spark plug(s). Torque the spark plugs to 13 ft. lbs. (19 Nm).
  2.  
  3. Install the ignition coil(s).
  4.  
  5. Connect the negative battery cable.
  6.  
  7. Perform system initialization procedure.
  8.  

 
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