See also:

Spark plugs
Be sure the engine and ignition switch are off and that the parking brake is engaged securely. Be sure to use the correct socket to remove the spark plugs. An incorrect socket can dam ...

Troubleshooting guide
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Octane rating tips
Using unleaded gasoline with an octane rating lower than recommended can cause persistent, heavy “spark knock”. (Spark knock is a metallic rapping noise.) If severe, this can lead to engin ...