What Generally Causes Air-Fuel Ratio Faults?
3 Answers
Accumulated dirt in the air filter clogging the intake passage, resulting in reduced air intake and an overly rich fuel mixture. Below is relevant information about the air-fuel ratio: 1. Introduction: The air-fuel ratio (A/F) refers to the ratio of air mass to fuel mass in the combustible mixture (A: air, F: fuel). It is a crucial parameter during engine operation, significantly impacting exhaust emissions, engine power, and fuel economy. 2. Principle: To achieve optimal exhaust catalytic efficiency (above 90%), an oxygen sensor must be installed in the engine exhaust pipe for closed-loop control. The working principle involves the oxygen sensor measuring oxygen concentration in the exhaust, converting it into an electrical signal sent to the ECU, thereby maintaining the engine's air-fuel ratio within a narrow, near-ideal range (14.7:1). If the air-fuel ratio is too high, while CO and HC conversion rates slightly improve, NOx conversion rates drop sharply to 20%. Therefore, ensuring the optimal air-fuel ratio is essential, with proper oxygen sensor operation being key to achieving this.
I often tinker with car engines, and air-fuel ratio issues are quite common, mainly due to sensor problems, such as aging or carbon buildup in the oxygen sensor. It monitors the oxygen in the exhaust; if the readings are inaccurate, the engine control unit can't adjust the fuel mixture properly. Clogged or leaking fuel injectors are also major issues—too much or too little fuel disrupts the balance. A dirty or faulty mass airflow sensor can cause incorrect air intake readings, and vacuum leaks allow extra air to dilute the mixture. Although rare, ECU software malfunctions can also occur. These issues may cause the car to emit black smoke, spike in fuel consumption, experience unstable power, or even trigger the check engine light. Regular sensor cleaning and using high-quality fuel can help prevent problems, but if issues arise, it's best to use a diagnostic tool to read the codes and perform targeted repairs.
After driving for over 20 years, I've encountered many air-fuel ratio issues, with oxygen sensor failure usually being the primary culprit—it accumulates dust over time and triggers errors. Carbon buildup in fuel injectors or aging seals causing leaks disrupt fuel control. In the air system, a dirty mass airflow sensor or cracked intake pipe leaks air, throwing off the air ratio. Cracked vacuum hoses are common in older cars, allowing extra air in and making the mixture too lean. Occasionally, the ECU acts up too. These faults cause engine shaking, weak acceleration, and odd exhaust smells. I make it a habit to check these parts every six months, especially before long trips—simple cleaning can extend their life. Don't delay if symptoms appear; early repairs prevent costlier damage.
