O2 Sensor Irratic Voltage Readings

[mjonesjr84]

I had replaced my O2 sensors in February with Walker units. Today my B1S1 voltage is all over the place. From 0 to 1.0 and everywhere between. I replaced it with another new sensor and it still does it. The Jeep seems to run fine, but MPG's are suffering and it has a rough idle. It's also throwing randomly a P0171. The cylinders 1-3 plugs were covered in dry black soot.

Is it the injectors?

 

[macleanflood]

Or a plugged cat or exhaust leak.

-Mac

 

[CharlesHS]

I had replaced my O2 sensors in February with Walker units. Today my B1S1 voltage is all over the place. From 0 to 1.0 and everywhere between. I replaced it with another new sensor and it still does it. The Jeep seems to run fine, but MPG's are suffering and it has a rough idle. It's also throwing randomly a P0171. The cylinders 1-3 plugs were covered in dry black soot.

Is it the injectors?

To determine if the injector(s) are part of the problem you can swap injector on cylinders 1& 3 with injectors from good running cylinders. If the problem moves to the previously good running cylinders and the previously good running cylinders are now not running properly; then the problem is the fuel injectors.
When was the last time the spark plugs were replaced ? Plugs can stop working properly even if they are several months old.

 

[mjonesjr84]

Or a plugged cat or exhaust leak.

-Mac

The downstream O2 reads fairly consistent .7-1.

To determine if the injector(s) are part of the problem you can swap injector on cylinders 1& 3 with injectors from good running cylinders. If the problem moves to the previously good running cylinders and the previously good running cylinders are now not running properly; then the problem is the fuel injectors.
When was the last time the spark plugs were replaced ? Plugs can stop working properly even if they are several months old.

The plugs and coil pack was 3 months old. I got a warranty coil pack and purchased 3 plugs for banks 1-3. The last time I got this code, I changed plugs and the coil pack and it solved the problem, for 3 months. Changing those didn't do anything.

I've read online that it has been solved with a new fuel pump. Mine is the original pump and I need to drop the tank to replace the skid plate. My plan was to replace the pump while the tank was down. I guess I'll be dropping the tank this weekend.

If the fuel pump doesn't do the trick, I'll swap injector locations.