drove the truck all day just fine but coming home felt a vibration in the motor like an out injector but didn't go away when i got on it. when i let out it got worse and felt like the truck was running on 4 cyls so i pulled over and shut it off a minute and started it but still bad so i punch the throttle hard once in park and it started running right again drove around another 15 mins then stopped for 15. went to leave again started fine drove fine for 2 mins then 4 cyl feeling again. went to back up a hill to turn around and it stalled. wouldnt start so i let sit for 5 mins and started but still running like crap so i punched it again but didnt work this time just stalled again. got it started again and limped it as far home as i could (i was only 2 miles away) but it stalled a few more times and was still crappy running started smoking white smoke on start up but went away after a few seconds made it half mile from home only because most was downhill and just rolled. felt like the motor hydrolocked two times but spun over after letting it sit. Any ideas on where to start?