Hello, All:

I have a problem with my 96 1.9L IDI Jetta. The engine sometimes
stutters or hiccups like one cylinder is not firing. It seems to
mainly happen while the engine is warming up, with the temperature
gauge just coming out of the hash marks (about 60 degrees C). It
starts just fine, even when the temperature is -35. And it runs just
fine at first, and generally runs fine after it's fully warm.

History:
It had a light case of the hiccups a couple of years ago in the
winter. I attributed it to bad fuel, put some fuel conditioner in and
never really noticed it again. It started to act up again this past
fall. Of course, there were some major hiccuping problems since there
was a burnt glow plug, but I replaced the plugs (well, the three of
them that you can actually get at and the third one was dead so I
stopped there). It is due for a timing belt replacement. Any chance
this is a timing issue? I guess I'll find out when I get that job
done. Anyhow, its done this over several tanks of fuel, so I'm
thinking that's not the problem, unless the first tank left some crap
behind. Fuel filter perhaps?

It was doing this the other day while I was idling in a parking lot.
Every few seconds it would stutter and a puff of white-ish smoke would
pop out the back. I had a look at the clear fuel lines for bubbles
and there were some teeny-tiny ones. I know that substantial amounts
of air in the fuel lines caused similar (though more severe) problems
in my old 87 TD when the engine totally shut down for a second or two.
Most disconcerting when you're cruising down the highway. Maybe the
size of the bubbles is related to the size of the problem. But why
does it mainly seem to happen at a particular temperature?

Anyhow, it does this while I'm driving around, and it's a big
embarassment to the VW community to have this Jetta jumping around
like a wild mustang and farting clouds of smoke. Anyone have similar
experiences? Your advice, please?

A/B