Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Oscilloscope Pattern Diagnostics (Spark Plug Faults)
2013 BMW 650i 2D CoupeSECTION Oscilloscope Pattern Diagnostics (Spark Plug Faults)
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- For evaluation of sparking period at idle, voltage peak No. 1 indicates normal ignition voltage peak. Spark plug is okay. If ignition voltage peak (voltage peak No. 2) is low, electrode gap is small. If ignition voltage peak (voltage peak No. 3) is high, electrode gap is too large. See Fig 1.
- For normal combustion and spark plug, see Fig 2. If combustion period is long, electrode gap is small. See Fig 3. If spark period is short, electrode gap is large. See Fig 4.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.