Poor Gas Mileage

• Oxygen sensors play a huge role in adjusting a vehicle engine’s air/fuel ratio, the combination of gas and air an engine burns to produce power. A faulty oxygen sensor may allow too much fuel to be added to the air/fuel ratio, resulting in poor gas mileage.

Increased Vehicle Emissions

• Oxygen sensors monitor and adjust an engine’s air/fuel mixture to ensure proper engine combustion, vehicle emissions and performance. A bad oxygen sensor can result in poor air/fuel mixtures or lean or rich fuel-injection delivery, all of which can cause improper or inefficient engine combustion and increased vehicle emissions.

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  A Typical oxygen sensor mounted on the exhaust pipe.

Rough Engine Idle

• Proper engine combustion is crucial for maximizing engine performance. A bad oxygen sensor can cause a car’s engine to idle in a choppy, rough manner. This is caused by the less-than-optimum engine combustion firings that result in poor engine performance.

Engine Missing

• If a bad oxygen sensor causes an engine’s air/fuel mixture to become too lean or restricted, the explosions within an engine’s cylinders (engine combustion) will be altered.

  

  misfire spark plug caused by a bad cat converter.

  Normally, an air/fuel mixture that is too lean (too much air, not enough fuel) will cause an engine to miss, or misfire, especially when an engine is idling.

Engine Hesitation

• Engine hesitation is similar to engine missing. However, engine hesitation is experienced only during acceleration, while an engine miss can be experienced both during engine acceleration and idle. A bad oxygen sensor may misread or misinterpret an engine’s air/fuel mixture or air/fuel requirements and cause too little or too much air and/or fuel to enter an engine’s cylinders, especially during acceleration. This can cause an engine to hesitate, or stumble.