a couple of things can mess up the cold running ...

- coolant temp sensor. little $15 gizmo on the thermostat. it's BLUE (NOT
  the silver one ... that's for the temp gauge in the dash). this tells
  the computer how "cold" the engine is, and how much to "choke" it. if
  this gizmo dies (and my 88 has had it replaced twice already), the bus
  will stumble and die at stop lights and just generally run like crap
  until it warms up.

- idle stabilizer valve ... this is the thingie in the air hose that goes
  from just behind the air flow meter (the silver box attached to the air
  filter box) to the rear (rear is rear) middle of the engine. it allows
  extra air to pass from the crankcase into the air intake when the engine
  is cold. it's supposed to close off as the engine warms up. if it stays
  closed all the time, the engine won't run worth a damn when cold.
  this thing is expensive. $179. :(  but it can be cleaned, with brake
  cleaner or other spray solvents. it's a sort of medium-sized cylinder-
  shaped gizmo with wires going to it. sort of bronze colored.

- O2 sensor dying. can also confuse the computer.

now, that's not ALL the things that might cause your problem, but it's the
three most likely (i think). my bet would be the coolant temp sensor.

good luck.
joel

Joel, 

Thanks for the info, 
one new part I forgot to list was the coolant temp sensor that was replace in
april.  The Van sat all winter and one cccold morning there was a puddle of
coolant under the van that I traced to the coolant temp sensor.  At first I
panicked and thought it was the heads, but luckily it was just this sensor.
 Does this mean it couldn't be this sensor? No, but I will leave that at the
bottom of the list.

This morning when I started the van it seem to run better.  Maybe the problem
is associated with the van sitting for long periods of time(10-14 days)
without running.  Would this fact point me to look at one thing verses
another ?

I guess I will try cleaning up the idle stabilizer valve and see if that
helps.

Once again, thanks.

Scott.