warm starting problem

[iandd]

hi first time so be kind or I wont come out to play again

I hope somebody has a clue to this when I start the car a 1.9 2001 passat pd
the engine runs at high revs with misfiring for about 20 - 40 seconds but not very high revs then settles down and is fine but it does not do this every time
I also get heavier than normal smoke on start up
thanks

[stonedagain]

Probably coolant temperature sensor.

[iandd]

Thanks I will give it a try