Black Smoke Coming From Astra 1.8 Exhaust

[MissyRee]

I've got a 95 1.8 astra sport with the eco tec engine. Having only recently bought the car i can only go on what i've been told about its past. The car had recently undergone some engine work as the belt snapped and did the valves. Everything was replaced with genuine GM parts according to the guy i bought it off saying that it had full head set with head being skimmed and
new belt kit with tensioners also being fitted. Every thing was fitted and run up and levels checked as they should've been (supposedly) and all seemed well with the car.
After purchasing the car i had to drive it 80 miles to get back home and it drove spot on with no probs at all. Since then on a couple of occasions it
has thrown smoke out of the exhaust, once little amount of blue smoke for a matter of seconds so checked the oil and was a little low so i topped it back
up to the level. Since then hasn't seemed to have burnt any extra oil off and hadn't suffered any more smoke incidents until last night when it almost
filled the car park up with smoke after opening it up through the bends, however it wasn't blue this time it was a dark blacky greyish colour.
I took the car back down the road at a steady 30 and the smoke stopped and it drove fine again.
The car itself doesn't lose any power or run badly but i want to get this problem sorted asap but dont really know which route to tackle first.

Does this sound very serious or are there possible (relatively) cheap and simple fixes for this problem?

Any help is much appreciated.

[bigboots]

Maybe it hasnt had a good thrashing for a while and just cleand out the crap in the exhaust,
Black smoke is a sing that it is running rich, this might be due to the way you were driving it up and down the box with lots of revs through the bends
The ecotech engines were prone to coolant temp sensor failure, this can cause it to run rich and eventually running problems

[Toureman]

Are you sure it was black smoke?

If your car had been parked in the car park all day the engine would be cold, all cars pump out condensation/steam white or grey coloured for a few minutes until warmed up.