this is a problem that is proving quite difficult to remedy.  I have an 81 Vanagon, 2.0 liter engine, and recently I stopped driving it, in fact have been forced to leave it in NYC - 300 miles from my home- as a result of this mechanical distress.  What happens to the rig is that once you been running it for about twenty to twenty - five minutes that engine seems to sputter, and not fire consistently anymore.  It will fire and then miss an ignition point.  So I will be jerking along down the road, and wondering what to do to fix it.  Initially I thought that it must be a bum fuel pump.  So I changed it over...now I have two working fuel pumps.  Next I thought I would swap out the plugs and wires...so I have done that.  I checked the points, and they are fine, at least I think that they are fine, and I even changed the coil.  All to no avail.  So I throw myself upon the mercy of the list, and beg for some suggestions.  What would cause this to happen?  I have not been able to figure it out for tha life of me.  Thanks in advance.

Earl
'81 Vanagon