The first 37,000 - 38,000 was good, some rattles and squeaks that still have not been resolved. Some of that front end shake that so many of these trucks have experienced.
Above that mileage (out of warranty), I have had several issues with odd tire wear (left rear), failed MAF sensor, and some drivability issues.
Started to have some cold start spark knock at about 40,000 miles. Took it to the dealer, was diagnosed as a vacuum or false air issue. Checked ALL vacuum lines, fittings, and intake gaskets with no change. Purchased my own PC based diagnostic software and interface. Was getting codes 171 (system lean bank 0ne), 300, 305, 306, and sometimes 307 (random/specific misfires).
Began checking coils, sensors, plugs (learned about the issues with them and was forced to purchase $300 removal tool and 8 new plugs) but made no difference.
Took it back to dealer for additional service, was told it had low compression on cylinder 7 and that I most likely had a burnt valve.
Brought back to dealer for head removal and valve inspection, but was told I had a bent connecting rod and that I should replace engine at a cost of $6,500.
Began engine tear down/diagnostic myself, found that the rod is NOT bent. Called dealer and spoke with service advisor and engine mechanic that did last diagnostic was told that the compression was ABOVE specs. Started me thinking about how to achieve higher compression when building an engine. That is achieved with tighter fitting pistons and rings that are taller then stock. Pulled piston 7, found the ring grooves had failed exposing a rather large porosity pocket that intersections the ring grooves.
Have tried several ford dealers for a replacement piston but it is in back order with no expected date of shipment. I have been forced to purchase a complete set of new aftermarket pistons at a cost of almost $500 and still have to re-assemble the engine.
Lets hope this fixes the problem, for now at least. (I feel a fix and ditch coming on)