the lac was sitting over a year i started it up ran 4 2hour no smoke i change the oil and filler now it smoke if sit 2 long 1999 cadillac deville i put it a machine and it said bad 7# spark plug
The valve seals may be dried out and cracked. This allows the oil used to lubricate the valve train to leak around the valve stems and into the combustion chambers and foul the spark plugs.
It's also possible that the piston rings are badly worn and are allowing oil to be forced into the combustion chambers.
