MaintenanceDiagnosticsFuel Economy

Signs My MINI Cooper’s O2 Sensor Is Going Bad

The oxygen (O2) sensor in your MINI Cooper keeps track of how much oxygen is in the Cooper’s exhaust. This information is used by the engine control module to make adjustments to the air and fuel that is introduced into the combustion chamber. If there is a problem with this mixture, you will notice the following signs of an O2 sensor going bad below.

Black Exhaust

One thing that can happen with a bad oxygen sensor is that the engine control module will put too much fuel in the combustion chamber. When this happens, the engine burns a rich fuel mixture, and you may end up with black exhaust smoke coming out of your tailpipe. The smoke is being caused by the excess fuel that is being burned in the engine.

High Emissions

This problem can also increase your MINI Cooper’s emissions, which will make it fail its emissions test. This is because the excess fuel that is being burned in the engine is releasing excess carbon into the vehicle’s exhaust. Consequently, a vehicle that is releasing too much carbon cannot pass an emissions test.

Performance Issues

Depending on whether the fuel mixture is rich or lean, you will also notice that you have engine performance issues. If the mixture is rich, your Cooper may surge forward even though you do not increase the pressure on the accelerator. If the mixture is lean, the Cooper will struggle to run, sputtering and hiccupping along the way. Your MINI Cooper might even stall.

Poor Gas Mileage

Either imbalance in the air and fuel mixture will cause poor gas mileage. This is because the engine is burning away excess fuel with a rich fuel mixture or working too hard to run on a lean fuel mixture. If you’re filling your MINI up more often, it could be because you’ve got a malfunctioning O2 sensor.

Sulfur Smells

The rich fuel mixture can also damage the catalytic converter. Once this happens, you will notice sulfur smells in your vehicle’s exhaust and coming from the engine. These smells are often described as rotten eggs, and it’s important that you get this problem checked immediately. Your engine may also overheat if the catalytic converter has failed.

Check Engine Warning

Finally, all of the above will trigger the engine control module to turn on the check engine light. This is because your engine isn’t running as it should be and the module has received error codes from various systems.

Lucas Auto Care in Cypress, TX, would be happy to test your MINI Cooper’s oxygen sensor to make sure it is working properly. If it isn’t, we can replace it.

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