Start with the application
Confirm the exact plug and specified gap for the engine or documented calibration. Factory pre-gapping does not remove the need to verify the intended application. Do not copy a smaller gap from a different engine simply because both are turbocharged.
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Measure gently
Use a suitable wire-style gauge and avoid levering against the center electrode or insulator. If adjustment is permitted, move only the ground electrode using the approved tool. Follow the plug maker’s limits; replace a plug damaged during handling.
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Diagnose before changing the target
An excessive gap can demand more ignition voltage and contribute to misfire, but misfire can have other causes. Record the fitted plug number, measured gaps and symptoms. Narrowing every gap without diagnosis can hide the original issue rather than fix it.
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Sources / references 1
- Manufacturer technical reference ↗Reviewed Oct 6, 2026
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