An internal combustion engine operates with a specific air-to-fuel ratio to achieve optimal performance. When the engine receives an excess of fuel relative to the amount of air in the mixture, it is described as operating with a fuel-rich mixture. A straightforward example is an engine that produces black smoke from the exhaust pipe, indicating unburned fuel being expelled.
Maintaining the correct air-to-fuel ratio is vital for fuel efficiency, minimizing emissions, and ensuring engine longevity. The condition where excessive fuel is present can lead to reduced fuel economy, increased carbon deposits within the engine, and potential damage to catalytic converters. Historically, adjustments to carburetors were a primary method for correcting imbalances, but modern engines rely on sophisticated electronic control systems for precise fuel delivery.