I took heads off my 4.6 yesterday and found the valves on the left side are very white. The pistons looked pretty normal though. THe valves from the right head were dark black and covered with carbon. The spark plugs are exactly the same color from each respective head. I took motor apart and found bad rod bearings but that shouldn't have anything to do with the heads/valve I wouldn't think. White makes me think it was running lean on that side, but what would make one bank be that lean and the other have carbon deposits? None of the pistons were white or steam cleaned. Any ideas what could have caused that? Ill upload pics when I can

 

Either is was running extremely lean ( clogged fuel rail , vacuum leak causing lean condition, coil not firing, etc)
or thas a helluva headgasket leak.

 

Here are some pics. I dropped heads off today at machine shop, wonder what they will find. Any one else have any ideas what could cause this?

 

The clean valves are normal, the dirty ones have been running rich. Did you have a check engine light on for 02's or running rich?

 

yes. check engine light was on for 02 sensor for that bank. Engine was making so much noise I didn't think much of it at the time, but could a bad 02 sensor make it dump for much fuel into that bank to make it that rich?

 

Depends on which sensor: Upstream sensor- definitely. Downstream sensor- no.

 

code was P0150 which I translated as Bank2 Sensor 1 . That would be upstream right?

 

That's the one

 

K I feel a little better now. That explains the jet black plugs and valves on that bank I guess

 

Yup! When you put it all back together, replace the front two O2 sensors and that will put an end to the soot in there. Good Luck man!