My wife and I just came back form a 2000 mile trip to NovaScotia, Prince
Edward Islands and to the Madeleine Islands. On our way up, in Maine
intermittently the car would start to jerk/hesitate. This happened not only
at high speeds. It was not the "Vanagon syndrome". I disconnected the
oxygen sensor and things got better. So I got a new oxygen sensor installed
in Nova Scotia. Car seems to be running ok again, although it felt just a
it off.
Then on our way home the hickups came back and it started to get worse. On
the border crossing back into the US, I barely made it through customs. The
car would still idle normally, but would choke as soon as I opened the
throttle.  By reving the engine and use of the clutch I was able to get the
car up to speed so we could keep going. We made it back to New Hampshire
but barely made up to hill to our house.
Yesterday I tried to figure out the problem. Now the engine wouldn't even
start. I took the spark plugs out. They were completely fouled. I installed
new ones. The engine starts up and idles normally, but again it seems to
hesitate and jerk and lower RPM's and low load. I disconnected the oxygen
sensor again and things seem to be a bit better. I checked timing,
temperature sensor, throttle switch, compression, all seems to be ok.

I assume the spare plugs fouled up because the engine was running too rich.
But why? Could it be that the oxygen sensor got damaged again on our way
home? If so, why?

BTW, I failed to mention that the engine developed a head gasket leak, but
it seem still small (barley lost any coolant on our trip). I was told that
the leak should not cause any running issues, at least as long as it
doesn't become a more serious leak.

Any help or tips what I should check are greatly appreciated.

Bruno
86 Vanagon Westy, 2.1 WBXwith Digifant