What happens if the spark plug operates at less than 700°F (371°C)?

When a spark plug operates at temperatures lower than 700°F (371°C), it can lead to a buildup of carbon on the plug. This occurs because incomplete combustion is likely to happen at such low temperatures, especially in fuel-rich mixtures. Soot and carbon deposits accumulate when the spark plug does not reach the optimum temperature needed to burn off these byproducts.

The optimal operating temperature of a spark plug is crucial for ensuring proper combustion in the engine. If the temperature is not high enough, these deposits can create performance issues, leading to misfires, poor fuel economy, and difficulties in starting the engine. The accumulation of carbon indicates that the combustion process is not functioning effectively, underscoring the importance of maintaining appropriate operating temperatures for spark plugs to promote efficient combustion and overall engine performance.