Can a Bad Oxygen Sensor Cause Black Exhaust?

Yes, a bad oxygen (O2) sensor can cause black exhaust to flow out of your tailpipe. This is because the O2 sensor is sending incorrect readings to your vehicle’s engine control module (ECM). When the ECM receives these readings, it will make unnecessary adjustments to the amount of air and fuel that is in the combustion chamber. Trinity Auto Care advises that if there is too much fuel in the chamber, you may end up with black exhaust. A malfunctioning O2 sensor will also cause the following.

Check Engine Light Warning

One of the first things that will happen if your oxygen sensor has gone bad is the check engine light will come on. This is because the O2 sensor has notified the ECM that it is having problems. When we run a diagnostic check to find out why your check engine light came on, the error code will point to the oxygen sensor.

Engine Performance Problems

You may also notice engine performance problems with a failing oxygen sensor. For example, if there is too much fuel that is causing black exhaust, it may also cause your engine to pick up speed in spurts. If the opposite is going on in the combustion chamber and there is too little fuel, the excess air will cause the engine and acceleration to lag and stutter.

High Emissions Levels

Vehicles in Minnesota are not required to have emissions tests, but a malfunctioning O2 sensor will cause excess carbon in your emissions and, if you live in a state that has emissions tests, your vehicle will fail. This is because there is excess fuel burning in the engine and the carbon is a byproduct of the burning fuel.

Noticeable Reduction in Gas Mileage

You will also notice that you aren’t getting the gas mileage you used to get if you have a malfunctioning O2 sensor. Again, any time the engine burns away excess fuel, you are going to go through a tank of gasoline or diesel fuel quickly.

Noticeable Rotten Egg Odor

Finally, a bad oxygen sensor can create problems for the catalytic converter. This exhaust system part is responsible for treating the carbon monoxide in the exhaust. If it is inundated with carbon monoxide, it can clog. If you have excess fuel, you have excess carbon monoxide. Consequently, you will smell rotten eggs in your engine and in the exhaust.

Trinity Auto Care in White Bear Lake, MN, and Blaine, MN, can help. We can replace your oxygen sensor if it needs it. 

Photo by Birdlkportfolio from Getty Images via Canva Pro

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