What is the potential problem with an engine running rich?

When an engine is running rich, it means that there is an excess of fuel in the air-fuel mixture that is being delivered to the combustion chamber compared to the amount of air. This imbalance results in several issues, with excessive fuel consumption being one of the most significant.

When there is too much fuel relative to the amount of air, the engine cannot burn all of the fuel efficiently. As a result, more fuel is needed to achieve the same power output, leading to increased fuel consumption. This not only affects the vehicle's fuel efficiency but can also contribute to higher emissions, as unburned fuel is expelled into the exhaust system.

Running rich can cause other problems as well, such as fouled spark plugs and increased carbon buildup, but the primary and most direct consequence is indeed the excessive fuel consumption.