the car will run like crap, (rich, with a miss), from cold start all the way to full hot, cruising down the highway.

then every once in a while, the SES light comes on, with a code44 (LEFT O2 LEAN) on Datamaster, and the car runs about 80% better. this just doesn't make sense. the car seems to be running rich, but the computer tells me lean??!!

where should i start replacing?:

-O2 sensors
-cap
-rotor
-wires
-plugs
-coil
-icm

My hypothesis is that the left O2 is bad (96k miles on it) and reading uber-low mV. so the ECM is dumping a ton of fuel into the left bank to compensate, explaining the black soot on the white bumper. The only flaw in this logic is that the car runs like crap on cold startup too, which is open loop, and unaffected by the O2.

I guess it's possible some plugs are fouled in addition to, and as a result of, the bad Ox sensor. That would explain crappy running when cold.

Also, I can record a run on Datamaster, if somebody can analyze it for me and tell me if one of the O2s is bad.

 

Try swapping the O2s.

 

That is one possible cause, however, a miss from something else(bad injector, ignition, ect.) will cause a lean code too.....how you ask, with all that fuel in the exhaust??, well, an O2 sensor senses just that, Oxygen, not fuel, so, you have a fuel/air(o2) mix going into the exhaust, all the extra o2 causes the o2 sensor to read really lean, might stay pegged(stuck) lean and set the code, so, swap the o2s if it has 2, if it stays, the o2s are not the problem, it is from a miss

 

one question:

swap O2s: as in move the left one to the right bank, and vice versa? or swap them both with new ones?

 

left to right and right to left, In theory the other side is know good