If too much fuel and not enough air reaches the engine, what may happen?

When an engine receives too much fuel and not enough air, it experiences a condition known as "rich" fuel mixture. This lack of adequate air causes incomplete combustion of the fuel, which can lead to several issues.

One significant outcome of this imbalance is that the engine may not start at all. When there is an excess of fuel, the engine can become flooded, meaning that the spark plugs can be coated in fuel and will not ignite, preventing the engine from turning over. This situation also disrupts the necessary air-fuel mixture ratio required for the engine to operate effectively.

The other scenarios provided do not directly relate to the issue of an imbalanced fuel mixture. While overheating might occur in various engine problems, it is not specifically a direct consequence of a rich fuel mixture. The transmission's failure would not be a direct result of a fuel and air imbalance and typically relates to the drivetrain or transmission system itself. Lastly, the vehicle running smoothly would contradict the reality of having too much fuel, which would generally cause rough idling or stalling rather than smooth operation.