When it starts smoking blue..does it also starts to run very rough??
Does it stongly smells like petrol?

I ask you this, because i had a simillar problem a few months ago.
The reason was a broken membrane in the fuel regulator. This causes an overfueling when the car runs on idle - due to the vacuum, petrol was sucked through the vacuum pipe of the fuel regulator into the intake manifold.

Sorry for my bad english - i am Austrian