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

3 Answers
JudahLynn
07/29/25 4:42am
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.
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JudahAnn
08/12/25 5:24pm
When I experienced a lean engine mixture condition, the car had absolutely no power during acceleration. Pressing the gas pedal felt like stepping on cotton, and the speed wouldn't increase. At idle, the entire vehicle shook violently – I could feel the vibration clearly in the driver's seat. There were several embarrassing instances where the engine suddenly stalled at red lights. After inspection, I learned the air filter was severely clogged, restricting airflow, and there might also be insufficient fuel supply from the fuel pump. Continuing to drive like this long-term would cause engine temperatures to rise, creating overheating risks that could damage cylinders and pistons. For safety, don't delay – I recommend immediately cleaning the fuel system or replacing components. Regular maintenance can prevent these issues and avoid unexpected breakdowns on the road.
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IsabellaLynn
10/03/25 3:56am
I encountered a lean mixture issue when driving my old Corolla. After starting, the acceleration felt sluggish, and when I pressed the accelerator hard, the car made a choking sound but couldn't speed up. At idle, the steering wheel shook violently, and items inside the car vibrated. I even experienced two unexpected engine stalls, requiring multiple restarts to get back to normal. I suspect it's caused by clogged fuel injectors or aging oxygen sensors. If not repaired promptly, it could also lead to increased fuel consumption. An unstable engine during driving is dangerous, especially when accelerating on the highway. I immediately went to a professional shop for inspection and cleaning, and with just a few simple steps, the smoothness of driving was restored.
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