A4 2.5tdi 2006, Lots of black smoke, loss of power

[mortoney]

It started couple of months ago. It was a bit of black smoke at beginning and it got to that stage that even after light acceleration extensive amount of black smoke comes out. With that also problems with power loss. Its fine when pulling off slowly, only very shaking could be felt. But if I try to pull off quicker, I get only loads of smoke and no power.
Today on the way to mechanic, car started shaking at idle, sounded like one of the cylinders misfiring and even more loss of power, like in limp mode. Mechanic told me that problem probably with one or more cylinders, probably compression and that it will cost a lot to investigate further, he suggested to me that I should rather try to get rid of the car, sell as it is.
I took car back from mechanic, on the way home, all came back to "normal", no misfiring and more power.
Now I am thinking that mechanic concentrated more on fact that engine misfiring and not on smoking. Could "black smoke problem" cause misfire of one of the cylinder for that moment?
Codes he found was about glow plugs.

I have visually inspected all pipes for air leaks, could not see anything wrong there.

What do you thing problem could be? or you agree with mechanic on this?

[Crasher]

That could be badly worn cams/lifters. Done professionally this is more than the car is worth but if it is a good car, it may be worth it to you.

[HAWKS]

Black smoke could be,badly blocked air filter,Injector fault or fuel pump fault.
Black smoke is normally over fueling or wrong Air to fuel mix.
Black smoke fuel related,Blue smoke Oil related and White smoke is Water related burning of.