On Mon, Jun 16, 2014 at 7:41 AM, Larry Alofs <lalofs@gmail.com> wrote:
I'll second what Mark said.  Typically after driving for an hour at steady
hiway speed, vanagon syndrome causes the engine to start to cut out for a
heart stopping moment or two, while driving.  Some times it gets worse,
sometime it clears up, especially if you change speeds.
   Since your problem is at idle, I would first suspect the idle switch.
 There should be two wires leading from it to a connector nearby.  If you
disconnect it there and test with an ohmmeter you should get some useful
info.  Set the meter to the lowest resistance range.  It should read close
to zero if you hold the leads together and some meaningless reading when
they are not touching.  Connect the leads firmly to the wires from the idle
switch and move the throttle away from the idle position and back.  The
switch should conduct electricity every time the throttle is closed,
reliably, whether closed gently or snapped closed.  The switch should not
conduct when the throttle is move a little off the idle position.

Good luck,
Larry A.

   Thanks,

   I have noticed a very slight hesitation sometimes when I resume throttle
after a downhill....the motor seems to be bogging a little just for a
second and then it catches and resumes normal running..This often happens
at the bottom of a gully after I have been off the gas for the downhill and
need to resume throttle for the uphill...

   Maybe I should just replace that switch, if I can determine exactly
which type I need and get the correct one...Every other part in the system
has been replaced and the older parts are living under my rear bench as
"iffy" spares, but I haven't swapped that throttle switch and it may indeed
be faulty.

  What exactly does a "throttle switch" do?

 Ahh!  , another clue is that the engine/exhaust has been increasingly
'popping' out the exhaust pipe on 'drop throttle', especially as the
vehicle is first started up but sometimes even when full temp.  I have been
thinking this popping is due mainly to an exhaust system crack near the
head pipe junction...but now that I think on it, there has to be excessive
fuel being drawn through the motor in order for it to ignite in the exhaust
system and cause that popping...and if the throttle switch does what I
think it does, it should be cutting the fuel off when the throttle is
closed, yes?