Ive done some searching and looking around but i wanted to get an opinion as i cant find a solid answer. Its a 99 f150 with the 5.4. Just bought it about 2 months ago and im starting to notice little things.

It has started to shudder slightly when i first crank the motor. its slight but noticeable and sometime goes away after it warms up. Today i go back from letting it sit over the weekend while i was out of town and it started right up, but... as soon as it started the shudder was significantly noticeable and it started dumping white smoke. After i let it warm up and drove it a little the smoke went away and the shudder seemed to settle down a little bit. What i have found is it could possibly be a sticky injector? Any opinions would be greatly appreciated. it currently has 158xxx miles.

 

Bad valve stem seals. My 03 does it if it sits for a few days.