What is a common symptom of a malfunctioning MAF sensor?

A malfunctioning Mass Air Flow (MAF) sensor can lead to improper fuel trim readings because it provides critical data to the engine control unit (ECU) about the amount of air entering the engine. This information is essential for the ECU to calculate the proper fuel-to-air ratio needed for optimal combustion. If the MAF sensor is not functioning correctly, it may report incorrect airflow information, leading to an incorrect fuel trim. This results in either a lean condition (too much air relative to fuel) or a rich condition (too much fuel relative to air), which can affect engine performance, fuel economy, and emissions.

While excessive engine noise, high idle speed, and increased exhaust emissions can be associated with various engine issues, they are not direct or primary symptoms of a malfunctioning MAF sensor. Excessive noise could come from other mechanical problems, while high idle speed could stem from issues like vacuum leaks or idle air control valve failure. Increased exhaust emissions may result from multiple factors, including mismanagement of the air-fuel ratio, but they are less specific than the fuel trim readings directly related to MAF sensor performance. Thus, the most reliable symptom pointing specifically to MAF sensor malfunction is indeed improper fuel trim readings.