What are the symptoms of an excessively lean air-fuel mixture in an engine?

[JudahLynn]

The symptoms of an excessively lean air-fuel mixture in an engine are: 1. An excessively lean mixture will cause slow combustion of the air-fuel mixture during the power stroke, resulting in continued combustion during the exhaust stroke. The burning gases enter the exhaust pipe, causing it to glow red. 2. At idle, the engine load decreases, the throttle opening becomes smaller, and the intake air volume reduces. At this time, the intake manifold creates a vacuum due to the reduced throttle opening, and exhaust gases can be sucked back into the intake manifold during exhaust, further reducing the oxygen content in the intake manifold. 3. If the fuel injection is too rich at this point, it will cause a significant decrease in the air-fuel ratio, meaning the gasoline proportion is too high. As a result, oxygen becomes extremely scarce, leading to very low combustion efficiency and poor fuel economy. Additionally, it can cause carbon buildup in the cylinders and spark plugs, preventing them from functioning properly.