Still broken :(

I also put on a new DPFE last night.  That was a horrible job (I just
hope I don't have to change the EGR, it seems like you'd have to pull
the motor to do that).  Who's clever idea was it to put the DPFE on the
rear of the motor facing the firewall?  I mean, AT LEAST use attaching
bolts that face the front of the engine bay where you can actually get
to them.  Oh well, there's another tool that's forever lost somewhere in
the engine bay :(  Now I'm all cut up and burned :(

Anyway, the new DPFE made no discernible difference either.

I have a replacement fuel filter to put on this weekend (that's one huge
mutha), but I doubt it will make any difference.

Is it worth trying a new fuel pressure regulator?  Would a faulty one
starve fuel so rapidly that the vehicle splutters and bucks?  Or am I
barking up the wrong tree?

There's also the possibility of changing out the CKP and the VSS
(although I have no idea where the VSS is on the 3.0 motor).  I'd rather
not spend more than I need to so if any knows if either of those
wouldn't help then let me know.  I'd expect a faulty CKP to throw a code
at least.

It has new plugs, new wires and a brand new MAF, much to the distress of
my wallet. No replacement fuel filter yet, but I wouldn't expect such
harsh symptoms from a dirty filter.

I just changed out the coil pack myself about an hour ago (for $64), and
drove back to work.  Okay so far, but then it can run fine for a while.

If it's still good after a week, I'll concede that the coil pack was the
culprit.  I'm not holding out much hope though, so I still preemptively
have replacement VSS and CPK sensors on my "to buy" list.

have you done the obvious like plugs, wires, and fuel filter? And clean
the MAF...? At your mileage it needs it anyway. Is there a certain way
to drive it to make it do it for a longer period of time to set a code?
If you can get it to do it long enough you will get a missfire code that
will point you to the right cylinder at least.

I have a 98 Windstar 3.0 with 128k miles on it, and over the past few
months it has had a problem with hesitation and bucking.  The problem is
intermittent.

My mechanic has diagnosed a few things so far and a lot of money has
been spent on 'repairs' but nothing he suggests fixes the problem.  I've
now taken it back from my mechanic and his "shotgunning" repair
technique in order to try and diagnose the problem myself.

So far I've replaced the Throttle Position Sensor and the Camshaft
Position Sensor, and while that seemed to fix it for a day or two, the
problem came back.  (It's intermittent nature means it can run fine for
days).

There seems to be no rhyme or reason to the hesitation, it can happen
when you're pulling away gently, or when you're cruising at highway
speeds, or during a shift, pretty much any time.  Turning overdrive off,
or keeping the transmission in 1st or 2nd makes no difference.  Also you
can drive it really hard sometimes without the problem manifesting at
all.  Often I'll drive it hard 10 miles to work and it's fine, then it
will act up on the way home with about 3 miles to go.

As good as I can tell it feels like the engine is cutting power to the
injectors or plugs all at the same time.  And the loss of power can last
from a fraction of a second to a whole second before it recovers.
Sometimes you just feel a bit of spluttering as though only a single
injector or plug isn't firing.  I thought it might be a transmission
problem, but I'd imagine that the revs would climb while the
transmission slips, and that's not happening.

I've also had poor idling on occasion, but it's very uncommon, so may
not be related.

Any ideas what to try next?