Well, after having enjoyed three months of hesitation-free, stumble-less
driving, the merciless and unrelenting vanagon syndrome has struck again.
This time, however, I am ready with the digitool I built. I put it in place
and am watching it closely while waiting for the problem to reoccur.

My temp 2 sensor, however, is reading 0.3 v when the engine is at its
normal operating temperature.  That seems rather borderline from what I can
find in the archives. I am thinking that it is right on the edge of
tripping the ECU into open-loop operation. Can anyone confirm what the
switchover point is?

I lost a couple of miles per gallon on my gas mileage beginning a few weeks
ago for no apparent reason. That seems to support the theory that the ECU
is intermittently going into open-loop mode and enriching the mixture.
Overall driveability has been good except for the stumbling and hesitations
that just occurred.

Regards.
John Clavin