Spark Plug Faults

Evaluation of sparking period at idling speed.

1. Normal ignition voltage peak Spark plug is OK.
2. Low ignition voltage peak Small electrode gap.
3. High ignition voltage peak Large electrode gap.

Fig 1: Evaluation Of Sparking Period During Idling Period

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Evaluation of sparking period at idling speed:

1. Normal combustion period:
   • Spark plug is OK
   Fig 2: Evaluation Of Sparking Period - Normal Combustion
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Long combustion period:

• Small electrode gap.
Fig 3: Evaluation Of Sparking Period - Long Combustion Period
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Short sparking period:

• Large electrode gap.
Fig 4: Evaluation Of Sparking Period - Short Sparking Period
Courtesy of BMW OF NORTH AMERICA, INC.