What symptoms might indicate that an engine is running too lean?

When an engine is running too lean, it means that there is not enough fuel in the air-fuel mixture, leading to a ratio that is too high in air compared to fuel. This condition can produce several noticeable symptoms.

Hesitation is often experienced during acceleration as the engine struggles to receive the necessary fuel to maintain power. Misfires can occur because the spark plugs may not receive adequate fuel to ignite, leading to incomplete combustion. Poor acceleration results from the engine lacking the power necessary to propel the vehicle effectively due to the fuel deficiency. Together, these symptoms clearly indicate that the engine is unable to operate optimally because of the lean condition.

In contrast, while increased fuel efficiency might seem beneficial, it is often misleading in this context as it can signal an improper air-fuel mixture. Excessive exhaust smoke would typically indicate a rich condition instead, while steady engine performance suggests that there are no issues at all. Therefore, the best choice that outlines the symptoms of a lean-running engine is the one that includes hesitation, misfire, and poor acceleration.