spark plugs sooty on one side - O2 sensor?

Question

My V6 started throwing error codes once warmed up: right bank lean trim differs too much left-right Engine seems to run okay though. So I checked out usual stuff. I found all the right side spark plugs are sooty, and the left side spark plugs have nice brown deposit. So I suspect the right exhaust oxygen sensor is crying "too lean" and the PCM is pumping too much fuel into right side. The sensors were probably never changed (it was a few years old when I bought it). There exists an error code meaning "no exhaust sensor" but that is not flagged. Is old exhaust sensor the common cause of this problem?

Also wondering, if there is unburnt fuel, will it wash oil away and cause accelerated wear?

Steve W. · Accepted Answer

Year, Make, Model, Engine? What are the actual codes that comes up?

Could it be a bad O2? Yes, Could also be a vacuum leak to the left side, Excessive EGR flow, Faulty wire harness, Leaking injector, partial converter blockage just to name a few.

Geoff Welsh · Answer

and to add;

The proper way to diagnose ONE suspected faulty HO2S would be to monitor them ALL simultaneously with a graphing capable scan tool and force the engine rich with propane and then lean with a vacuum leak. Observation and comparison tells the tail.

I suppose the backyard way would be to switch the left and right ones and see if the other side's plugs turn black...have fun GW

spark plugs sooty on one side - O2 sensor?

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