GM Service Manual Online
For 1990-2009 cars only

Tools Required

J 39358 Spark Plug Socket

Service Precautions

    • Allow the engine to cool before removing the spark plugs. Attempting to remove the plugs from a hot engine may cause the plug to seize, causing damage to the cylinder head threads.
    • Clean the spark plug recess area before removing the plug.
        Failure to do so can result in engine damage due to dirt or foreign material entering the cylinder head or contamination of the cylinder head threads.
        Contaminated threads may prevent proper seating of a new plug.
    • Do not install the plugs that are either hotter or colder than the heat range specified.
        Using plugs of the wrong heat range may damage the engine.

Removal Procedure

  1. Turn OFF the ignition switch.
  2. Notice: Twist the spark plug boot one-half turn in order to release the boot. Pull on the spark plug boot only. Do not pull on the spark plug wire or the wire could be damaged.

  3. Remove the spark plug wires using a twisting motion in order to release the boot from the spark plug.
  4. The spark plug wires are numbered to assist in re-assembly.

    Notice: Use the J 39358 or the equivalent. Failure to do so could cause cracking of the insulator and arcing inside the plug, resulting in engine misfire.


    Object Number: 172979  Size: SH
  5. Remove the spark plugs using the J 39358 .
  6. Inspect each plug for wear.
  7. Refer to Spark Plug Visual Diagnosis .

Installation Procedure

    Notice: Be sure plug threads smoothly into cylinder head and is fully seated. Use a thread chaser if necessary to clean threads in cylinder head. Cross-threading or failing to fully seat spark plug can cause overheating of plug, exhaust blow-by, or thread damage. Follow the recommended torque specifications carefully. Over or under-tightening can also cause severe damage to engine or spark plug.


    Object Number: 172979  Size: SH
  1. Install the spark plugs.
  2. Tighten
    Tighten the spark plugs to 15 N·m (11 lb ft).

  3. Install the spark plug wires in their original locations.
  4. Refer to Spark Plug Wire Harness Replacement .