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Q: Fuel burning rich, black smoke

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Black smoke and plugs getting black. What can cause this.
My car has an automatic transmission.

A: As you may know the oxygen sensors which ar...

As you may know the oxygen sensors which are part of your emissions system read exhaust gases to determine whether or not the appropriate amount of oxygen is present in the exhaust. Based upon this reading, this information is relayed to the car’s ECU which then makes a determination as to whether or not to add more or less fuel to the engine.

When too much or too little oxygen is present, this will cause Check Engine Light to come on. Too much oxygen may be present in the exhaust gas due to things like an exhaust leak, a vacuum leak, a faulty mass airflow sensor (causing a lean fuel condition), or faulty fuel injectors.

To little oxygen may be present in the exhaust gas may be caused by things like a clogged air filter, a failing mass airflow sensor (causing too much fuel to be introduced to the motor), bad fuel injectors, or a clogged catalytic converter. When the O2 sensor is not working properly, this will cause false readings to be relayed to the computer causing inaccurate adjustments to be made to the intake and fuel system in your engine.

If you’d like to get this fixed, I would suggest having an expert from YourMechanic come to your home to diagnose the smoke firsthand to determine a solution and repair.

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