Often giving the float bowl a few taps can be enough to free off a sticky float. As it's come on so quickly, it does suggest something is stuck open somewhere - may be some crap has been pulled into the carb causing the float or butterfly to stick open.
The smoke may be a result of the car idling at 3000rpm rather than a symptom! I know when I've got my tick over up too high I get dieseling when I shut off - anything above 1000rpm can cause it on mine..
