From http://autos.groups.yahoo.com/group/vw-camping/
Part I, our vanagon trip on the way to Yellowstone:
At home I did a nice tuneup, the usual, spark plugs,
rotor, distributer cap, air filter, and all looked
good. Bosch fuel filter only had about 5k on it.
Vanagon was running great.
Made it across Snoqualmie Pass in Washington,
then when we reach the Idaho border, all of a
sudden there is some bucking and hestitation
every time we go up a hill.
It started after we got some Conoco gas.
East of Spokane they sell only Conoco, Exxon, and
a few unknown brands, but no more Chevron or Union 76,
our two favorites.
I replace the Ecu with a newer spare one.
For awhile the bucking disappears, and we continue
driving on east towards Yellowstone.
While crossing the Continental Divide in Montana,
(around 8,000 ft), we fill up with Exxon.
Now the bucking gets really, really bad.
Sometimes the vanagon comes to a standstill,
with the engine backfiring and sputtering.
Turned it off for 10 minutes, and it runs ok
again for another 50 miles, unless it goes steeply
uphill.
About 100 miles outside Yellowstone, the vanagon
backfires, then stalls, totally obnoxious behavior.
At this point, we are so close to seeing Yellowstone,
we don't want to turn around.
For the last 300 miles, I've tried various fixes
to try to figure out what is wrong.
I hook up the digitool (thanks Darrell for the
digitool), and everything checks out ok.
The fuel pump is pressurizing the system, which also
has a relatively new fuel pressure regulator.
The afm works good (with cap fix).
O2 sensor has good numbers.
Fuel pump relay ok, injectors are firing, throttle
switches good, temp 1 & 2 good, etc, etc.
Fairly new distributor with hall sensor.
All grounds are good, and no vacuum leaks.
There is no reason the vanagon should behave this way.
So we think maybe it's bad gas.
They do add 10% ethanol to some grades of gas in
Montana. So we pour in several bottles of Heet and a
bottle of a cleaner.
Vanagon starts to run a little better, with fewer
bouts of hesitation.
In Yellowstone and the Grand Tetons, we criss-cross
the parks up and down the mountains at 8,000 ft
altitude, and never have any more trouble.
So at that point, we think the vanagon is fixed,
and that it was just a batch of bad gas we picked up
somewhere.
In the park, we fill up only with premium grade, since
it supposedly doesn't have ethanol in it, which
could conceivably contain water, and cause stumbling.
At this point, we have a ample stash of gas dryer
bottles onboard, and periodically add a bottle to the
tank.
Next Part II, on the way back home
Harald
'90 vanagon westfalia

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