Engine running rough V6 2010

[Mel16]

Hi, I have a 2010 v6 commodore that keeps intermittently running rough, it comes up with an engine light, blows black smoke and smells really bad of fuel inside the car. Only happens once every couple of months though and everytime I take it into a mechanic they can’t get it to fault again or find any codes. Has anyone heard of this before?

 

[lmoengnr]

If the Check Engine Light is on, it will leave a code.
Your mechanic needs a decent scan tool to read the codes.