What is the method for diagnosing a lean fuel mixture fault in an engine?
2 Answers
Here are the symptoms of a lean fuel mixture in an engine: 1. A lean fuel mixture may cause popping or backfiring sounds. 2. The vehicle lacks power and is unstable, with difficulty increasing engine speed after starting. 3. In severe cases, it can lead to weak acceleration, rough idling, stalling during startup, and jerky gear shifts. Here are the main causes of a lean fuel mixture: 1. The primary cause is insufficient fuel injection. 2. Various intake sensors fail to accurately detect the air intake, resulting in insufficient fuel injection. 3. Excessive carbon buildup can absorb the injected fuel. 4. Failure of the oxygen sensor's closed-loop control. 5. Inaccurate detection of air intake.
Over the decade of driving my old Jetta, I've mastered the signs of a lean fuel mixture. The most obvious symptom is when flooring the accelerator during hill climbs yields no power, accompanied by backfiring from the exhaust and raw gasoline fumes. At red lights, idle RPM would suddenly drop below 500, feeling like it's about to stall. An old mechanic once taught me a field trick: unplugging the oxygen sensor when the engine's warm—if the idle stabilizes, it's almost certainly a lean mixture. Modern cars are smarter; the dashboard reveals clues—long-term fuel trim values exceeding +10% are dead giveaways. This issue needs immediate attention, or both the oxygen sensor and catalytic converter will be ruined.
