My cars smell like burnt candles!

I have a 1995 Olds 98 and a 1998 Olds 88. Both cars emit a burnt candle smell - usually following a hard stop. Sometimes you can even see a puff of smoke. It does not smell like burning oil or antifreeze. I do not notice it much in the summer when the car heater is off. Does anyone have a clue to what this is? I would greatly appreciate any help.

Please tell us where the “smoke” emanates from.
Bear in mind that this could be steam instead of smoke.

Is it coming from:

under the hood?
the exhaust pipe?
the car’s undercarriage?
the HVAC vents in the cabin?
underneath the seats?
the instrument panel?

The smoke or steam is outside the car - from the front end or under the hood. I have always suspected that the smell was coming in through the vents, but you can smell it outside the car (in the front) as well. Pinpointing it has been difficult because it disipates quickly, and when I open the hood I don’t see any evidence of it. We had a mechanic look at the car a couple of years ago, and he thought it was exhaust backing up. It doesn’t smell like exhaust.