12 13... Spark-Plug Faults

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2005 BMW 745i, 2005 BMW 745Li, 2004 BMW 745i, 2004 BMW 745Li, and 2003 BMW 745i. However, it is still accessible from the selected car via links, so may be relevant.

Evaluation of sparking period at idling speed.

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

Fig 1: Evaluation Of Sparking Period During Idling Period

Courtesy of BMW OF NORTH AMERICA, INC.

Evaluation of sparking period at idling speed:

Normal combustion period:
- Spark plug is OK.

Long combustion period:

Small electrode gap.

Fig 3: Evaluation Of Sparking Period - Long Combustion Period

Courtesy of BMW OF NORTH AMERICA, INC.

Short sparking period:

Large electrode gap.

Fig 4: Evaluation Of Sparking Period - Short Sparking Period

Courtesy of BMW OF NORTH AMERICA, INC.