Are you measuring the O2 sensor voltage with it connected in an operating
engine?
  If the voltage is a "steady 0.55V" there is something wrong in the
system.  The voltage should be going up and down between about 0.1 and 0.9V.

Larry A.

On Mon, Jul 7, 2008 at 1:49 PM, Walter Houle <whoule@ecscontrols.com> wrote:

> Good news - I passed Test Number 4! NOx at 15 & 25 MPH went from 1497 to
> 1074 and from 1090 to 326. The CO & HC numbers went slightly up and are
> now "average".
>
> I spent a day checking everything and found two likely causes: The first
> was a split connector on the aux. air regulator intake hose. The other was
> an exhaust leak right at the flange where the two exhaust header pipes
> combine into one. This was about 4" from the O2 sensor and was most likely
> throwing it off. I installed a new O2 sensor. The old, (almost new) one
> read from 0.48 to 0.52 V so it was probably OK. The new one read a steady
> 0.55 V after the fixes. I installed some rebuilt injectors for good
> measure. I didn't change the catalytic converter, but it is still suspect -
>  I just squeaked by with my 15 mph NOx number. Maybe next year. For the
> record, it was made by Magnaflow.
>
> Thanks to all who answered - you gave me plenty of ideas and I learned
> lots in the process. I am still kind of amazed that 2 local VW mechanics
> didn't have the gumption to check for something as simple as intake &
> exhaust leaks first. The $320 they cost me sure was a waste of time and
> money!
>
> Walter
> 85 Vanagon 1.9L
>