Hello,
I have a 2003 Lincoln Aviator, which I believe is in need of another engine. I was getting some knocking noise from the front of the engine. The car still preformed well while this noise was happening. It would be loud while the car was idle (it sounded a if i had a diesel engine under the hood). Well this occurred for a couple of months. I even took it to our local ford dealership but they could not diagnosis the noise? Well the engine finally called it quits and stopped running. Funny thing is, it acts as if it wants to crank but will not stay started. Could this be the timing chain? where the guides are broken? Could a Ford Explorer engine be installed in a Aviator?

It is certainly possible to be the timing chain. Quick way to verify if it is attached is to take the valve cover off or look through the oil cap maybe and see if the valves are moving. If they are, the next trick is the timing at the right time.