My 1990 Aerostar (the type with the larger engine) was running great,  Nice and
smooth, good MPG, peppy as they get.  Has been well maintained.
Then it needed an new alternator.  Still ran fine other than the things that a dead
alternators cause.

I had the alternator replaced.
It has run like %$#%#  since then.  The check engine light comes on after 5 miles.
The engine sounds OK for maybe 2 seconds and then makes sort of a lunging sound, like
it is revving up and letting off.  Over and over. It sounds like a engine would if a
person was pressing and letting up on the gas pedal.
It hesitates when I take off  from a stop.  It is more likely to die if I take off
fast.

The car repair guy has spent hours trying to figure it out.  He and his guys ran
diagnostics. Found nothing other than an oxygen sensor.  Had that replaced.
He sounds quite frustrated.  I think he has done his best.
Don't think he want to ever see the thing again.
Last we spoke, he suggested that I take it over to a Ford dealership to see what they
can figure out.
Am hesitant about that because of previous experiences with dealerships.
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Other info:
I went over a big bump.
The Check Engine light remains off after I stop the van for a short while, but comes
back quicker when I start it up again.
It passed Washington State emissions test, running as it is.  Check Engine light was
on.
I asked if it could be a vacuum leak.  Mechanic said he thought not.
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I really need to get this thing running properly.   Don't want to throw more money at
it unless is warranted.

Thanks!!

Red