Learning summary: Hotter weather and the associated mechanical
expansion/contraction and corrosion has been triggering electrical contact
failures in many list vans in the past several weeks.  Coils, AFM, throttle
switches, others.

One PREVENTATIVE measure is to clean connector contacts by
1)pushing connector on and off or
2)clean contact by scraping with something like steel wool
then mate the connector with a little contact grease like the formula made
for spark plugs.

The story below shows how the digitool can catch some contact problems
and can prevent big trip disasters and high cost troubleshooting
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Symptoms: Started south from Sacramento on warm June 11 day.  Temp 2
started at 1.1V cold and nicely declined to .21.  In heat of San Joaquin
Valley sometimes reading would jump from .21 to .35 to .5 to .21 then
after a while stabilize at .21.  Between LA and San Diego in stop and go
traffic, jumped to .95V while stopped. Could barely get the van to move.
Should have checked O2 right then but didn't. Went back to .21.  Slight
correlation of voltage bouncing around with road roughness, and problem
seemed more likely when engine or outside temperature was higher.

Research:
1)Read the Bentley diagram and Temp 2 location and removal.
2)Very helpful list member (that I was trading shocks for hubcaps with)
  pointed out location of  Temp 2 since I'd never touched it
3)Consulted the oracle of vanagon fuel injection (Darrell Boehler)
  about the problem.  Darrell noted that the feedback loop opens with
  Temp 2 above .3 v which is very bad since the engine will run rich.

Most likely (and easiest to fix) theorized failure mode:  Connector contact
slightly  intermittant (higher resistance sometimes which would cause the
symptoms) due to corrosion, vibration and heat.

Experiments:
1)Had son watch reading while jiggling the connector.  No change.
2)Unplugged Temp 2.  Digitool reading 4.5V (!)
3)Plugged Temp 2 on and off about 20 times, put some contact grease
  on (thank you Debi), drove 2000 miles to Austin without a flicker of the
  Temp 2 reading.

See PREVENTATIVE measures in the Learnings summary at the beginning.
Key learnings for me:
1)Every couple of years clean and put a tiny amount of dielectric grease
  (to keep corrosion elements like oxygen out) all
  interesting looking electrical contacts.  Haven't done that yet since
  am still on a trip and don't want to break something that currently works.
2)DIGITOOL: DON'T LEAVE THE DRIVEWAY WITHOUT IT!  It pointed to the problem
  before the van performance had given any symptoms whatsoever.
3)I'm real appreciative for all the help from the list.  The combination of
  about 10 people's inputs, plus knowing far more than I ever wanted about
  connector failure mechanisms at work, really nailed this problem at the
  start and added one more item on my long preventative maintenance list.

Given the vanagon caused chaos that has taken place on some other trips,
I'm thrilled to have....

Ducked a big one, Tom Neal '87 syncro