What could a malfunctioning spark plug result in?

A malfunctioning spark plug can lead to difficulty in starting the engine. Spark plugs are crucial components in the ignition system, generating the spark necessary to ignite the air-fuel mixture within the engine's combustion chamber. When a spark plug is faulty—whether from wear, carbon buildup, or damage—it may not produce a strong enough spark, or may not spark at all. This directly impacts the engine's ability to start, as the necessary ignition of the fuel will be compromised.

The other choices indicate outcomes that are typically associated with a well-functioning spark plug. Increased engine power and better fuel economy are results of efficient combustion, which a faulty spark plug would hinder. Similarly, increased airflow into the engine does not relate to the operation of the spark plug, as that aspect pertains more to the intake system rather than ignition. Thus, the primary consequence of a malfunctioning spark plug is indeed difficulty in starting the engine.