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Hey Cody, I hope I can help, my '16 XLT was doing the same thing. It was a cracked plug. The crack was so small you couldn't see it without really looking at it. So I had the dealer put all new plugs in when I had the 100k maintenance done. Less than 5k miles later I was getting the same behavior and a misfire on 3. Dealer changed the plug, it was cracked (a brand new plug) fast forward another 15k miles and it did it again. But no codes. I found a really good mechanic and he said Fords are notorious for having engine issues and trying to correct for it without throwing a code. So he dug out all six plugs and found cracks in two of them, I think it was on 2 and 5. So he put all new ones in and it fixed the issue and my mileage went back up. Apparently, the engine will misfire enough times the engine will basically shut down that cylinder, which is why your mileage drops. And these engines run at such high pressures, just knocking a plug against the block accidentally can be enough to cause a crack later on. Out of the 6 the dealer put in my car, 3 ended up cracked. Call it dealer idiocy, touchy parts or whatever, it's an issue that wasn't too hard to fix on my truck.Attached are some pictures.