Neon smoking from vents

I have a 1998 neon sport, I recently bought it from craigslist I dont know to much about it, but..........
The other day it was sitting their idling, I had the heat on also set to circulate within cabin. Anyway when I got in the car it had filled up with smoke???? I checked the temperature it was normal. I have no clue why this happens... PLEASE HELLP
milage is 130,000
fresh oil and plugs,
coolent looks good and full,
no mods stock 2.4L dohc
motor is sound running with no ticks or miss fire
The old plugs where white but not damaged or fried.
The smoke was Blueish in color like oil burning ??

SOLUTION- Valve cover gasket leaking oil onto engine causing smoke.