12 13 ... Further Fault Patterns With Evaluation

Evaluation of sparking period and ignition voltage peaks at idling speed:

1. Normal combustion period.
2. Normal ignition voltage peak.

   Ignition system is OK.

Fig 1: Evaluation Of Sparking Period & Ignition Voltage Peaks At Idle Speed
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Long sparking period (1) with low ignition voltage peak (2).

Indicates low compression.

Fluctuating sparking period:

Indicates contamination on spark plug (shunt).

Fig 2: Long Sparking Period With Low Ignition Voltage Peak

Courtesy of BMW OF NORTH AMERICA, INC.

Short sparking period (1) with high ignition voltage peak. Constant but short sparking period:

Indicates defective ignition lead.

Fig 3: Short Sparking Period With High Ignition Voltage Peak

Courtesy of BMW OF NORTH AMERICA, INC.