Black Smoke is mostly unburnt fuel and/or poor timing.
_DARK_ grey smoke is usually contaminated fuel or a very small amount
of burning oil mixing with contaminated fuel. When is the last time you
drained the water out of your fuel filter?
_LIGHT_ grey smoke is usually burning oil to a serious degree. If you
are burning a very large amount of oil, the smoke will be a dense,
white, stinky mess.
Smoking when accelerating could be bad timing as well.
_White_ sweet-smelling 'smoke' is usually burning coolant.

Suggestions:

a) make sure that the timing belt is good and within its service
interval, and that it has not skipped a notch.
b) change your fuel filter if more than 30K miles (45km) old. Drain the
water in any case.
c) run a can of Techron, or if you can find it Chevron DELO fuel
additive through the system. Follow the directions on the container.
Fill up with fresh diesel fuel when you do this.

You may also have gotten some high-paraffin diesel (high-wax content),
AKA "summer fuel" and/or additive-free heating oil. That stuff _WILL_
smoke although in theory it should do no harm to the engine. What
happens is that suppliers sometimes (rarely but it happens) mix up at
the yard, especially if tankers do double-duty, delivering heating oil
some days and diesel some other days. The sovereign cure for this is to
add a few gallons of kerosene (up to 1/3, as it happens) to thin out
the diesel. NOT GASOLINE. NEVER gasoline. This also helps with winter
starting although your mileage will drop some.

Peter Wieck
Wyncote, PA