Hi all!
Was hoping someone had some insight on my engine codes, all signs point towards an O2 sensor failing but there's also a misfire code and I'm not sure if they're related but they popped up around the same time. hopefully its just the sensor and I dont have to replace the injectors and/or coils. Also I'm getting a hard start when the engine has warmed up.

2002 Qx4
codes:
P0301
P0158
P0159
P1167

Thanks!

Many solutions for the Pathfinder will apply to your QX4.
o2 sensor?
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got code p0301
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Help! Code P0301 Cylinder 1 Misfire 2000 QX4
Fixed P0300 Multi Misfire / Now Have P0302 Cyl 2 misfire

Thanks for the links, I'd already read some of those and read a few more. None seem to have the 02 sensor codes and the p0301 at the same time. I'll just assume they're separate issues

The P0301 is a misfire on cylinder 1 which most likely is either a faulty spark plug,
faulty ignition coil or clogged or faulty fuel injector.
Cylinder 1 I believe is on the passenger side and is the first bank nearest the radiator.

I would pull the spark plug on cylinder 1 and see what condition it is. If it looks good it most likely is a bad ignition coil. Many people will swap the coil on the cylinder that has the misfire with another cylinder and will
see if the code follows, for example if you swap coil 1 and 2 and then you get a P0302 code that tells you that the coil that was on cylinder 1 is bad.

Is the engine running rough?

Thanks, yeah the engine isn't running rough but I'm getting a hard start after the first drive of the day and sometimes a stutter when idling. Just bought it about a month ago so I'm going to replace the plugs anyways. And check the power valve screws, that one scared me after reading it could run your engine!?

In case anyone else runs into a similar situation it ended up being a bad spark plug tube seal. The spark plug in cylinder 1 was coated in oil and after pulling the valve cover it was obvious that the seal had failed/cracked. It's unserviceable so I've got to pony up for a whole new valve cover...ugh

Try some ultra black RTV in the cracks around the tube seal.