My '08 Explorer has a 4.0 SOHC engine on which a plastic guide on one of the front timing chains flew apart two years ago. I replaced all of the front chains, guides, sprockets and tensioners at that time, to the exclusion of the rear one. It ran ok until recently when it refused to start, acting as though it wanted to hit and might occasionally start, but wouldn't accelerate or idle and ran roughly until it would promptly die. After running the battery down a couple times I decided to put on a new fuel pump; that didn't help. Then I put on a new fuel pressure sensor; that didn't help either. Fuel filter is also new. Reluctantly, I decided to pull the timing cover again only to find that the crank, balance shaft, and both cams are all in time. It appears I've reached the pinnacle of my shade tree mechanic skills on this project. I've yet to put it back together, as thought I'd throw the question out there first in case the answer lies within the mind of real technician somewhere. Any suggestions on what to try next will be appreciated.