Seems exactly the same Problem!!
Last summer roughly from July to September.
Starting acted intermittenly . But when I
just put there for a couple of days , it
worked again.
Finally, when I traced all wires according
to Haynes Manual, I found it seems that the
Diode (located in Engine Compartment Fuse Box) maybe the cause. But when I test it
with an Ohmeter, it seems not bad with a very
small reisitance in one direction and an almost
blocking resistance in the other direction,
which is a Diode should be.
When I shortcut the Diode, everything seems OK.
btw: This "bug" costed me over $300 to get the
starter replaced, which didn't help at all.
I consulted at least 3 mechanics, they
surprisingly agreed on their judgements
of my weak starter. And finally I followed
one of them and get the starter replaced,
which they claimed, is really a challenging
job for a mechanic.
Damned Ford!!