Any wisdom on O2 sensors?

[Rich <mrich@xxxxxxxxxxxxx>]

    Can someone give me a brief rundown on what role the Oxygen Sensor
plays in overall vehicle performance.  I have been experiencing symptoms
of a lean fuel mixture, loading-up, hesitation and black smoke at
take-off, etc...(after she warms).  I bought the '84 528e a few weeks
ago, and recently noticed that the O2 sensor was disconnected (probably
intentionally).  Prior to reconnecting it, I had only driven the car a
few times, and only short distances.  It seemed to run fine.  When I
drive longer distance, the above occurs.  I guess my question is, will
replacing the sensor help to correct this problem, or at least be part
of a remedy with other things to consider as well?

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