What could lead to a lean running engine?

A lean running engine occurs when the air-fuel mixture has too much air relative to the amount of fuel being supplied. This condition can arise from multiple factors, and each of the aspects mentioned contributes to this scenario.

Restricted air intake can hinder airflow into the engine, potentially reducing the amount of air available for combustion. While it might seem counterintuitive, if the air supplied becomes limited while the fuel remains constant, the mixture becomes richer. However, if there's no corresponding adjustment in fuel delivery, this can lead to compensatory lean conditions in certain operating scenarios due to engine management systems attempting to achieve the ideal mixture.

Low fuel pressure directly affects the volume of fuel that reaches the combustion chamber. If the pressure is insufficient, the fuel injectors cannot spray the correct amount of fuel into the intake manifold, resulting in an imbalanced mixture that can lead to a lean situation.

Faulty fuel injectors can also create a lean condition. If the injectors are clogged or malfunctioning, they may deliver less fuel than required. This inadequate fuel delivery means that, again, there is too much air in relation to the available fuel for combustion.

Thus, all of these factors can independently or collectively contribute to an engine running lean, which is why the answer