Borrowed a friends autotap and it shows misfires on driverside. 02 sensor problem maybe? No codes.

 

Did it show which cylinders were misfiring?

 

Why would you associate misfires with O2 sensors?

Misfires occur in the cylinders well before the O2s sample the exhaust gasses.
Misfires can be ignition related, fuel related, or valve train.

sparkplug wires
sparkplugs
coils
injectors
bent pushrods
bad lifters
broken valve spring

 

Faulty O2 sensors certainly can cause misfire issues.

If all cylinders on one bank show misfires (current or history), and O2 sensor or clogged catalytic converter are likely causes.

Exactly which cylinders are misfiring and what is the count on each?

 

Yes, didn't say that they couldn't, and you'd have an O2 code or codes along with the misfire code.

If you have a misfire why not look to the simplest most likley suspect rather than jumping to conclusions?

 

With the information you gave us it could be a million things, scan it and tell us what codes it's throwing, obviously P0300 is going to be one of them.

 

Read the original post.

O2 sensors can fail without setting a DTC. Misfires can occur without setting a DTC. Converters can fail without setting a DTC. We need a misfire count - all GMs have a misfire monitor that is easily read in Mode 6 data.

 

speaking of checking fuel and injectors, how do you check the injectors? I need to troubleshoot mine because i threw an rear o2 code despite the fact i'm running in batch-fire mode and i suspect fuel problem but I cant find a way to get an electrical ohm reading without cutting into the injector wires? is there an easy contact access for a voltmeter?