Eric,

The engine runs fine right after I start it back up.  Then the rough running
starts again, with black exhaust.  I am going to check out the O2 sensor,
coolant sensor, vacuum lines, and air mass sensor first.  I'll keep you posted,
after I do some tests.  Do you know where the coolant sensor is located.  I've
also had problems with bad connections, since the Vanagon has been setting for
over a year without being started.

Thanks,

Charles