Skip the auto shop - Our mechanics make house calls

Q: Misfire caused bad o2 sensor?

asked by on

when i bought the car they said it had misfire when i checked engine light code came back as a o2 sensor

My car has 106000 miles.
My car has an automatic transmission.

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 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.

To avoid unnecessary repairs, I would suggest having an expert from YourMechanic come to your home to properly diagnose your misfire issue and fix it accordingly.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: How do you get access to replace the O2 sensors on a Audi A6 4.2 engine? There does not appear to be any room?

Hello. In order to remove the oxygen sensors, you will likely need an offset oxygen sensor wrench. An offset oxygen sensor wrench will be compact enough to fit into low clearances but still provide enough torque to break the sensors...

Q: Starts fine but immediately when I turn off the engine, it won't start again until I count to 60 and then it starts and runs fine. Repeats.

Hi, thanks for writing in. The problem is most likely caused by the ignition control module. It would need to be verified by inspecting the spark when the problem happens. If you would like help, consider having an expert automotive...

Q: Engine misfiring p0300 code

Hello there, many faults will cause a random misfire in your 2004 Chevrolet Classic. Replacing the spark plugs is the first step so it's great you have taken care of that already. A few other faults will cause cause a...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...