primary O2 sensors

[burt ragio]

Do the primary O2 sensors switch back & forth to control air fuel ratio or do they control each bank separately ?

[alec2538]

The O2 sensors switch in RESPONSE to changes in A/F ratio, which is controlled by the PCM. They don't "control" the ratio, they confirm it.

Each bank is monitored and adjusted individually.

[JohnE]

Both sides of the engine (banks) fueling are controlled separately. The powertrain computer (EEC-V) increases fuel until the primary O2 sensor gives a "switch" feedback. And it also decreases fuel after the switch until it gets another switch feedback the other direction. The O2 sensors switch at stochiometric for the combustion result.

The computer learns biases in the form of short term and then long term trims for each bank. These learned values are then used in the fueling calculations as a new starting point.

[burt ragio]

No engine light or codes. With an occasional engine stall at idle & one entire cylinder bank running lean, what is most likely the probable cause vacuum leak or O2 sensor ?

[martyo]

No engine light or codes. With an occasional engine stall at idle & one entire cylinder bank running lean, what is most likely the probable cause vacuum leak or O2 sensor ?

Data log the 02s make sure they are switching.

My bet is a vacuum leak.

[RF Overlord]

Marty, we put my Actron code scanner on it and the O2s are switching...the only odd thing is the LTFT on bank 2 is at 8.6%, where B1 is only 2.3%. I know neither of those numbers is especially high, but it's the imbalance that I was curious about.