At 12:20 AM 9/23/2002, Dave Baker wrote:
>I had been getting 19-21 mpg right up until the head gasket failure.  Did
>the PO have some sort of magic wand to make the van run so well without an
>O2 sensor or is something hopelessly jimmied up?

The lambda sensor / O2 sensor is necessary for proper operation of the
catalytic converter -- but if the AFM is in good adjustment it's not
necessary for good running of the vehicle.  Any Vanagon operated in Europe
/ Great Britain / most of the world before unleaded fuel became widely
available either was not supplied with a sensor or had it removed along
with the cat. convertor as a tank or two of leaded gas would destroy them both.

OTOH the lambda sensor can backstop the rest of the system and allow good
running even if the AFM is not quite right, there are minor vacuum leaks etc.

OTOOH the sensor will *cause* running problems if there are exhaust leaks
upstream or near the sensor, as oxygen enters the system through the leaks
and makes the sensor believe that the engine is running lean.  And it can't
compensate for differences between cylinders.  If there's any oxygen in the
exhaust it causes the mixture to be richened until the oxygen is gone or
the ECU runs out of adjustment room.

david

--
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"