Trouble after Trans Rebuild 2015 5.3

[Adam Ferguson]

So I had my Trans rebuilt.  When the builder test drove it after rebuild he left a o2 bank 2 sensor unplugged.  He Drove it for a few miles before truck stared running bad, idling bad, smoking and threw p0300 misfire code.  I think this was because it ran really rich because of the missing o2 on one side.  We have changed the plugs they were wet as can be. It idles better but still smokes and low on power. Still has p0300.

 

 Next steps are to change all four o2 sensors. I think I might have to replace the catalytic converters as well due to over fueling. I think this is the power issue.  

 

Question is anyone ever experience this or feel like it could be something else? 

 

 

 

[chadman]

Random misfire code will usually not be caused by O2 sensor faults.  Most defective O2 sensors will not cause drive ability issues on a new vehicle; it will simply ignore the zero reading and user other O2 sensors and data to compensate for it. If it was a downstream O2 sensor(after catalytic converter) that has zero effect on drive ability; its only purpose is to monitor cat efficiency.

 

Cats can be damaged by over/under fueling and is why they fail 90% of the time.  But a road test with an unplugged O2 would almost certainly not cause that issue that quickly. Someone that knows what they are doing needs to watch misfire monitors, check for vacuum leaks, and monitor mass airflow, etc.  Mass airflow sensors are notorious for going bad on these trucks, are often the underlying cause of transmission failures.

 

Classic clogged cat issue is you can drive it, but can not build any RPM's, or pickup speed (feels like it runs out of gas at 30-40 mph, or so).  Easy way to check this is remove your upstream O2 sensors(ones before the cats) and drive it.  If power comes back, and you can build RPM's, then you likely like have clogged cats.  If you have clogged cats, you need to find out why or it will happen again.