Q: I have misfires and cylinder 7 is not firing properly. Also the oxygen sensor needs to be replaced or sensors where is that locate

Misfiring can cause unburned fuel to enter the catalytic converter where it will light off in the converter, overheating it and melting the catalyst. Therefore, it is recommended that misfiring be repaired promptly. Causes of misfiring range from ignition to fuel system faults but there can be engine damage, such as to the valves, that will cause misfiring. Oxygen sensors should be carefully tested on an automotive scope before they are condemned. Just because an oxygen sensor is identified in a diagnostic trouble code as a "potential" fault does not always mean the sensor itself has failed. Wires to the oxygen sensor can get damaged and/or other problems in the engine can cause the sensor to report values to the PCM that are out of range. Oxygen sensors are installed in the exhaust manifolds and/or exhaust pipe very close to the manifold as well as post-catalytic converter. If you desire that the misfiring problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request an engine misfire diagnostic and the responding mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic.