E30 Zone

Hi - I've just discovered the cause of rough running and idle of my E30 325i - either I left the filler cap off or it worked it's way loose. Either way - I feel a twat - thought it was the plugs! So - the car has never smoked ( burnt oil ) before but now - if I stop the car after a drive - then start up again within about 30 mins, clouds of blue smoke... if I leave it for a few hours - no smoke. Doesn't burn any when driving or under load. Could this be to do loss of vacuum when the cap was off - somehow oil getting past the guides? Will I have done serious damage?

Worried of Devizes..

Update - seems to have cleared up, so hopefully no major damage.

If you've driven with the oil cap off, you will have sprayed a film of oil everywhere under the bonnet. The smoke was probably this burning off the hot parts.
The fuel mixture would have been weak with the cap off, which will raise the combustion temperatures, and could eventually do damage, but highly unlikely is this sort of time frame.