Oxygen Sensor

[parishht]

If it is the sensor, then search on google for cleaning the sensor.

Family Handyman or Mechanics Illustrated did a story on how to clean the sensor,
because some unscrupulous mechanix where charge for a new one with installation,
when in fact it just needed a good cleaning.
It is a piece of wire tha gets a shelac coating on it and when the coating gets too think,
the electronics think it to be bad.
It will affect your milage, if I recall from the article.