I am planning to be in Daytona week of 2/17. Since you can start it and it
runs for a short while I would look at the O2 sensor circuit. Since the
sensor being connected or not is not making much of a difference you need to
look for a shorted input wire and/or a bad ground.

The green wire for the sensor is actually a coaxial wire. There is the inner
signal wire and the outer shield which is connected to the chassis. You want
to strip the wire end so that both of these are accessible.
Now get your digital multi-meter. Key on, engine off, (KOEO), check the
center wire for voltage. The sensor goes to an amplifier input. You should
see some voltage, ~.6 volts between that wire and the chassis. If not either
the wire is not connected to the ECU or it is shorted to the outer shield.
In this case the ECU will continue to richen the mixture looking for that O2
sensor signal. Run away rich and black smoke. Now check the outer wire.
There should be "0" volts or real close to it. If there is any significant
voltage here that is a problem. Any voltage there will get added to the
reference voltage and the ECU will look for an O2 sensor voltage of ~.5 plus
that reference float.  This ground is shared with the distributor hall
sensor ground. On many vans this is connected at the base of the oil
breather. The plastic breather does not make a good contact point. Move it
something metal on both sides. I often use the fuel pressure regulator.
Also, make sure that ring terminal is actually making a good connection to
the wire. The black and oxidized wire itself is also a problem. Time for a
new ring terminal with a heat shrink sealed end. With key off you can also
use an ohm meter to check the outer ground path. Get back to us when both
the inner and outer wires are confirmed good.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
TJ Hemrick
Sent: Tuesday, February 4, 2014 5:06 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Rough running, black smoke, running rich, no idle

All,
  87 Vanagon GL, 2.1, Auto.  Water pump gave up the ghost-fixed that,
starter issues-finally got a good one, now the beastie won't idle to save
it's life.  If I disconnect Temp 2 it idles at 1800 rpm (smooth as silk) no
matter what else (even the air screw in the throttle body completely
closed).  New Temp 2 sensor-no change.  O2 sensor, no change connected or
not.  Starts smooth but within minutes, runs really rough, misfires, running
*super* rich (black smoke).  Any thoughts or suggestions?