i HAVE A f-150 6CYL WHEN YOU LET THE TRUCK SEAT AND IDLE AFTER 3-4 MIN THE SMOKE STARTS GIVE IT GAS AND IT GOES AWAY THIS DOES NOT HAPPEN ALL THE TIME IT SEEMED AS IF I MAY HAVE HAD SOME BAD GAS HAD THE PINGING BUT NO LONGER HAVE THAT SOUND THE TRUCK HAS 116,500 MILES

 

If you have leaky valve seals it usually smokes at start up (blue smoke) then goes away. Black smoke means it's too rich and white smoke usually means coolant.