I  have a problem with my 1985 Vanagon camper.  It usually occurs on long
trips when the gas is at a quarter tank or lower, but it has also happened
at the half tank mark.  It usually happens when going up a hill.  What
happens is I lose the power to accelerate.  When I try to accelarate, a
violent jerking occurs.  The problem usually goes away after turning off the
van, only to recur a couple of hours later.  I have explained the problem to
several mechanics, but they haven't found the cause.  Has anyone experienced
a similar problem and know what causes it?

Thanks,

Linda Barry