Timing chain/cam phaser rattle on start up if it sets 3 days ('12 f-150 3.5 Ecoboost). I have a warranty on it from the car lot for a few more months and thought I might get it addressed, but I understand that Ford says that some amount of rattle is "normal." I was asking to see if anybody had run into that from a dealer. I took it to the guy that does things I can do and he said to take it to a Ford dealer. But he said they may say it's normal. It's also normal for some Toyotas as well. Only rattles for a second or two until the oil gets around the phasers. I found what it does, but didn't want to drive to a Ford dealer and spend money. If they were just gonna tell me it's normal. Not uncommon with that design.
when you next start it, hold the accelerator to the floor and crank it. It won't start but the oil pump will run and pre-lube the timing chain. Then start normally. See if this cures the initial rattle.

