Disconnect the O2 sensor and try it.  If it runs smoother....bad O2

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I wasn't going to reply until I saw this post because, altho' my symptoms were similar, I connected my driving in wet conditions to the problem described.

During what turned out to be an adventure (or excruciatingly horrible experience -- my wife's opinion), we were about 150 miles from our home in Columbia, MO, when the engine started "cutting out"; it would just quit. No pattern to the quitting, so hard to relate to any conditions I had knowledge of. I found that I could depress the clutch (of course), key off, key to start and sail on 'til quit, then repeat procedure. My BW put up with this for a while, then, after a couple of jerks and raggedy re-starts, she would have no more, her stress level was sky high, and the ride home was in the seat of a roll-back with '86 Westy behind us. Turns out that the wires to the not-even-previously-connected O2 Sensor were dangling, and, apparently the wet conditions enhanced the chances of the wire contacting some other metal part of the car. This may or may not be a logical explanation for the symptoms, but tying up the still-disconnected wires to the O2 sensor seemed to keep the symptoms from returning. This was on '86 #2, and #3 has Sensor connected as God and VW intended.

Jack Botts

'86 Vanagon Westy Weekender (#3)

'14 Passat TDI (sigh)