My vanagon is depressed and does not want to go anywhere.   So how do I cheer it up?

It will idle smooth as silk, but when asked to actually move, the van seems to have no power.  And I am not talking about it being
slightly sluggish.  It has almost no power.  It can barely make it up the hill that I live on - I shutter to think what will happen
if the wind changes direction.  On the highway I maybe can hit 40 on a flat surface.  But when idling it sounds good.

Any ideas?

Paul Borghese