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Coked lubricating oil on spark plug insulator. Could also be paint or other conductive material. |
CONDUCTIVE CONTAMINANTS ON FLASHOVER PORTION OF INSULATOR. Paint, coked lube oil, grease and other conductive materials can cause misfiring by promoting flashover. Make every effort to keep the flashover portion of the spark plug insulator clean and free of conductive contaminants. |
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Heavy residue of gray-colored or copper-colored compound in threads. |
EXCESSIVE APPLICATION THREAD LUBRICANT. Too much thread lubricant can eventually cause problems. Though thread lubricants can have anti-galling properties if used sparingly, too much can allow an excessive increase in the clamping force and this can make the spark plug impossible to remove. If heavy quantities of thread lubricant have been the practice of spark plug installation, we recommend that the carbonized residue be removed from the cylinder head's spark plug ports at each plug change by using a thread chaser/seat cleaning tool or a full bottom tap. If solid-state ignition systems are being operated, special care should be taken to remove carbonized thread lubricant in the port threads. This material can add resistance to the ground return circuit of the ignition system and can affect ignition performance. |
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