What to Do When the Engine's Air-Fuel Mixture is Too Lean?
2 Answers
An excessively lean air-fuel mixture is often caused by low fuel pump pressure. Dirty or clogged fuel injectors, or faults in the control circuit, can also lead to a lean mixture. Poor signals from the intake pressure sensor may result in fluctuations between rich and lean conditions. It's advisable to check the data stream to observe changes in injector pulse width and oxygen sensor voltage. Additionally, test-drive the vehicle to see if there's a noticeable lack of acceleration, combining diagnostic tool readings with driving conditions. The primary cause of a lean mixture is insufficient fuel injection, specifically: 1. Faulty intake sensors that inaccurately measure air intake, leading to inadequate fuel injection. 2. Excessive carbon buildup that absorbs injected fuel. 3. Failure of the oxygen sensor's closed-loop control. 4. Inaccurate detection of intake air volume.
A couple of days ago, I also encountered the 'engine running lean' warning light. After some troubleshooting, I identified a few key points. The most likely cause is an intake air leak, especially in older cars where rubber hoses may have cracks, allowing unmetered air to enter. Spray carburetor cleaner at pipe connections - if the engine RPM suddenly rises, that's your leak spot. A dirty oxygen sensor can also send false data; in my case, replacing the O2 sensor fixed it. Low fuel pump pressure is another suspect - hook up a pressure gauge, and if it's below 300 kPa, that's probably it. Clogged injectors are less common, but cleaning them never hurts. Here's a pro tip: in winter, the air-fuel mixture naturally runs leaner due to cold temperatures, so don't panic at the first sight of a trouble code.
