I will post this as i never read about it, I was having that problem, Shacking (feels like it was running on 3) when i cold started my truck. But it would shack for 10-15 sec then all would be good. Once the truck was heated up it wouldn't do it again when starting. I was suspecting air un the fuel, but i was wrong.
It turns out it was the glow plug, one must have not been working and it wouldn't heat up the precombustion chamber and that is why it would run rough at the cold start. I changed the glow plug but i think my problem was corrosion on the steel rail connecting the 4 glow plugs.
So if you truck ever shack or run on 3 at cold start but not after it is hot. Check the rail, or the glow plugs!
It turns out it was the glow plug, one must have not been working and it wouldn't heat up the precombustion chamber and that is why it would run rough at the cold start. I changed the glow plug but i think my problem was corrosion on the steel rail connecting the 4 glow plugs.
So if you truck ever shack or run on 3 at cold start but not after it is hot. Check the rail, or the glow plugs!