If your car, truck, utility vehicle, or van’s oxygen (O2) sensor is going bad, your check engine light may come on. The check engine light will come on because the sensor has sent an error code to the engine control module. It will also come on for the following reasons listed below, which Mark’s Auto Service explains are also signs of a bad O2 sensor.
Black Engine Exhaust
The oxygen sensor is located in the tailpipe so it can keep track of how much oxygen is in your automobile’s exhaust. It sends these numbers to the engine control module so it can make adjustments to how much air and fuel are in the combustion chamber. If the O2 sensor sends an incorrect reading, the module may send too much fuel into the engine. This will cause black exhaust as the engine burns away the excess fuel.
Because there is too much fuel in the combustion chamber, your vehicle will fail any emissions test it takes due to excess carbon, which is a result of burning fuel, in the exhaust. This can be caused by a failing oxygen sensor, a failing mass airflow sensor, or cracked fuel injectors among other issues.
Depending on whether there is too much air or too much fuel in the engine, you will notice that your automobile’s performance is compromised. When there is excess air in the combustion chamber, your vehicle’s acceleration and speed suffer. You may find that your vehicle is slow to respond when you accelerate and it will stutter and sputter as you pick up speed. If there is too much fuel in the combustion chamber, your vehicle will surge forward.
Poor Gas Mileage
A failing O2 sensor can also affect the gas mileage that your vehicle gets. If the engine is burning excess fuel, you’ll run out of fuel more quickly. If it is struggling to run because it doesn’t have enough fuel, you will still end up with poor gas mileage because the engine will burn the fuel more quickly.
Rotten Egg Odors
Finally, in the case of the engine control module sending too much fuel into the combustion chamber, this puts unnecessary strain on the catalytic converter and it might fail. If it does, you will notice rotten egg smells coming from your engine and in your vehicle’s exhaust.