First post on this: I have a 2007 Expo EB 5.4 3v 2wd, 112000mi. About 2 months ago I started experiencing hesitation in all gears while driving. I took it to Ford dealer with no answer. I replaced all plugs and COPs, no change. I then replaced vct solenoids, no change. I then replaced oil pump, phasers, chains, tensioners, guides, gaskets, & seals. I inspected the cams and journals, roller followers, and old timing components. Only thing bad was old tensioner seals but I replaced all these parts. I put everything back together(using all the pricey OTC tools and the Ford manual) and changed the oil, no change! I replaced both camshaft sensors, still no change. No codes were ever thrown, and now I'm into this thing for a large chunk of $ with no solution. The hesitation is less obvious when cold, but becomes very pronounced when engine is hot. It's not making any funny noises and will idle all day. Hesitation only while driving/accelerating. Can anyone suggest another path I should be investigating? Please help!
Also: I used Motorcraft filter & 5w20 semi-synthetic Motorcraft oil. I changed fuel filter and air filter. Fuel pressure and oil pressure are within specs.

 

Not saying for sure or not, but last year I had the same symptoms and it turned out to be a porous cylinder head leaking,

 

Thanks What is the resolution to a porous cylinder head and how do you identify it?

 

I have the same issue with my 2010 Expedition EL 4x4 (141K). Runs fine at idle and actually runs fine under moderate acceleration, but under heavy acceleration, it begins to struggle, almost like its missing. I changed out all of the coil packs and plugs, ran some injector cleaner through it and it hasn't changed anything. I was thinking it was possibly the injectors themselves and was going to replace them next. I really wanted to see a solid answer to the problem first before I continue to throw money at it.

One thing I've noticed is the fuel mileage has dropped over several miles per gallon since we purchased it with 70K on the clock so that's what got me thinking it may be the injectors going bad. Very frustrating...

 

I had the same issue. It wound up being a failed cam follower and worn cam shaft. I did however have a noisy valve train.