Volvo: Black smoke, oxygen sensor, meter check

Question
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Followup To
Question -
My volvo is starting to produce black smoke when i restart it after driving for a while why? please help.
Answer -
Does the black smoke go away eventually, or does it continue the whole time you remain driving the car?  Does the performance and sound of the engine change at all when it smokes?
Question -
The smoke does continue, but  the perfomance and sound of the engine does not change it does not lose power. It runs normaly except for the black smoke.

Answer
You might have carbon buildup in your engine which burns to a black smoke.  There are a variety of cleaners that can be used if that is the case, but you'll want to check with your mechanic before trying one of them.  It also could be that the car is running rich due to a failure of the oxygen sensor or the air mass meter.  Check to make sure those are working properly.  Good luck!