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Q: P0302 code/CEL. Spark plugs could be cause but not sure

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Car is sluggish on acceleration at low speeds. Runs great on highway. Rough idle. sometimes the CEL goes away for a few days and then comes back. Sometimes runs better when listening get is on. Never changed spark plugs as far I can remember.

My car has 153000 miles.
My car has an automatic transmission.

A: This code relates to a misfire which may be...

This code relates to a misfire which may be caused by many different reasons. This may be caused by faulty spark plug wires or plugs, a faulty coil pack, faulty O2 sensors or potentially a dirty or clogged fuel injector. The symptoms you describe seem to indicate a faulty O2 sensor due to the sluggish condition. 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 the 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 air flow 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 air flow 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. I would suggest having an expert from Your Mechanic come to your home to diagnose your emissions system.

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