Hi Paul --
At 01:41 PM 4/26/2009, Paul Connelly wrote:
>waiting for replacements to arrive). Checked the voltage output from the O2
>sensor (disconnected) and just wildly varies from about .05V to about .15V,
>nowhere near the .45V ish that it should be (or the .8V to be running that
>rich).

The half-volt signal is actually driven from the ECU -- on the naked
sensor will generally be either full high or full low or
transitioning between the two.  .05-.15v all counts as "lean" but
isn't meaningful otherwise.

If it's behaving the same way when it's hooked up, the ECU will drive
the mixture extremely rich trying to get the sensor to flip over to "rich."

>So seems to be O2 is at least the most likely culprit.

If that's how it's behaving when it is connected then it is without
question a culprit.

>get the first trip in next weekend, and would rather replace it than just
>leave it disconnected to get a better idea of how she is running overall.

If you want to know how the van is running, leave the sensor
disconnected.  It can cause problems, and it can disguise problems,
but it won't make a properly running engine run any better.  The sole
reason it's there is to tightly control the mixture for the benefit
of the catalytic converter.  So my advice would be at the first sign
of any running trouble, disconnect the sensor first, and don't
reconnect it until the problem is solved.  Your emissions will
temporarily go up some, but you'll be able to solve the problem
without the sensor sticking its oar in and confusing things.

  --
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'89 Po' White Star "Scamp"