What is a consequence of a fuel filter being restricted?

A restricted fuel filter can significantly impact engine performance due to reduced fuel flow to the engine. The fuel filter's primary function is to remove contaminants from the fuel before it reaches the fuel injectors or carburetor. When the filter becomes clogged, it limits the amount of fuel that can pass through, leading to inadequate fuel delivery to the engine. This situation can manifest as a lack of power during operation, particularly under load, because the engine is not receiving the necessary amount of fuel to generate the required power output. Therefore, option C correctly highlights the most direct consequence of a restricted fuel filter, affecting the vehicle's overall performance and driveability.

While the other options describe symptoms that might be associated with various engine performance issues, they do not directly relate to the primary effect of a restricted fuel filter, which is the restriction of fuel flow leading to power loss.