Hi,
I have a '83 1.9L watercooled that recently failed the hydrocarbon test
for CA SMOG. CO levels passed.
I just installed a new O2 sensor, but no change.

Engine runs fine at highway speed, but there is a noticeable pulsing of
the exhaust at idle, almost as if one of the cylinders was not fully
combusting.

Valves appear to be properly adjusted and cylinder compression appears
to be within spec (lowest was I think around 120).  I can check again
since I have the tool.

Any ideas on what to look for?

If I can't fix this, in the next few days, I'm going to bring it into a
mechanic.  I'm thinking about Fred's Garage in Redwood City, CA.  Any
recommendations?  I live/work in Palo Alto, CA, so there is Ole's Garage
near my office, but I don't know if he is a VW man or not.

I would love to take it to Ben's place in Sacramento, but it's a bit too
far for me to drive there with my wife and drop off the van.

But, hey, there is also the slim chance that i'll find the problem
myself (with the help of the friendly people on this list).

Peace and Thanks.
-- Craig