What would be a common symptom of a faulty spark plug?

A common symptom of a faulty spark plug is engine misfiring. Spark plugs play a crucial role in the ignition process by providing the necessary spark to ignite the fuel-air mixture in the engine's cylinders. When a spark plug is damaged or malfunctioning, it can lead to inconsistent or weak ignition, causing the engine to misfire. This misfire can manifest as rough idling, decreased power, or hesitation during acceleration.

In contrast, options indicating increased fuel efficiency or longer engine lifespan would not be associated with a faulty spark plug; in fact, a malfunctioning spark plug can lead to poor combustion, resulting in decreased fuel efficiency and potentially harming the engine over time. Similarly, silent operation does not correlate with spark plug issues, as a misfiring engine often produces abnormal sounds or vibrations. Thus, experiencing engine misfiring is a clear indicator that there may be a problem with the spark plugs.