What can cause Volvo v70 to be smoking black

 

Assume you are referring to a gas engine. Black smoke means your car is not efficiently burning all the fuel. That can be caused by weak spark, an overly rich mixture, low compression or oil consumption (if smoke is more gray/blue). First thing to do is have the car scanned for any check engine fault codes. There are quite a few possible causes that would be hard to diagnose without fault codes or additional tests.