Timothy--

A couple of things come to mind:

How long has it been since you had a "tune up" (plugs, cap, rotor, maybe
wires, etc.)? If the O2 sensor was unplugged, why? It may need replacement.
18 mpg isn't all that great. Pretty consistently, Vanagons in good tune get
20 mpg. 10% off isn't out of the question if you were hauling your National
Geographic Collection, if you weigh 650 lbs., and you have five adult
malamutes that go with you everywhere. But I suspect ignition stuff (+ O2
sensor) is to blame.

The fact that it is an intermittent problem will make it more fun for you
to figure out. You should be thankful for this additional challenge.

G. Matthew Bulley
Bulley-Hewlett & Associates
Cary, NC     USA
www.bulley-hewlett.com
(888) 468-4880 toll free

<<<SNIP>>>
My van is getting around
18mpg and everything seems fine.  The power is all there and all seems
to work fine.  I drove it to VT for school and when you get up to around
60mph or more it starts to give this sluggish stutter and if you take it
out of gear it idels between 1000 and 1500 very jumpy idel..but then the
idel will calm down and all will be ok for awhile.  The other thing is I
noticed that if im going uphill and keep my foot on the gas its normally
ok but if I let up just a little it'll start acting all crazy and make
me slow down.  The van does not do this unless the engine is warm.  I
took it to town the other day and once it warmed and I was moving at
about 50mph it started doing it.  This is  only an intermittent problem
because it will go away for an hr at a time.

Things I checked were gas which was all good....and my mpg which seems
to be fine.  All gages seem to be reading right and oil is very clean.
I did check the O2 sensor..it was unplugged so I plugged the wire back
together but it did not fix the problem.  <<<SNIP>>>

Thank you
Tim G
<<<SNIP>>>