[Vwdiesel] runs rough when cold

[Smith, Michael]

OK, admittedly, I haven't even checked the fuel filter to see if it's dirty
or anything.
When I start Bondo Golfy and warm it up for say, 1 minute or so, then take
off down the road, it "bogs out" (in lieu of a technical term) when revs are
probably (I'm guessing) above maybe 2500rpm. (worse under load).
If I am going up a small hill or whatever, it's a little worse and I am
"forced" to change gears earlier than normal...  Once I am down the road 5
kms and the temp guage is starting to rise up around the 1/4-1/3 mark (when
@ full warmth its just below the 1/2-way mark) the engine runs normally with
no bogging out...and I can really rev it out.

It almost feels like (if this were a gas car) like it has bad plug
wires....or maybe starving for fuel.  It's not "jerky"...just goes from say,
full power to half power when revs get high when car is cold. (if that makes
sense)

Only when the car is cold.....outside temps don't seem to make any
difference It's been -25*C to a balmy +10*C with no real change...other than
perhaps slightly longer to get to "warm" when it's really cold outside.

Is it a bad fuel filter?

I'm on my 2nd tank of fuel. First tank had a little gasoline added (about
when I reached 1/2 a tank).  No difference at any time. Car has been plugged
in,a dn not plugged in overnight with no real difference.  Ran old sloppy
oil, new 15w40 oil and now 5w30 synthetic oil.  No diff.

Mike in NB