On Mar 21, 7:56 pm, ahaysoali...@aol.com wrote:

Altitude?

Sounds like a job for Stephen King...

Seriously, I used to have a Buick Regal that would shut down after it
had been driven an adequate distance AND when getting off the
accelerator to exit a freeway.

The Buick dealership couldn't find it.  I called the zone representative
( I am sorry that Buick has made that option extinct) and he
knew the problem immediately.  There was a TSB on it (which the
dealership chose not to read).   A new computer put me back in
business.

Yours may be any of a bunch of things, but I would advise you
look through the TSBs for your car as a starter.

That reminds me of the infamous Vanilla Ice Cream story.
BTW - snopes.com reports that this is a true story. FWIW

Vanilla ice cream == car problems??

For the engineers among us who understand that the obvious is not
always the solution, and that the facts, no matter how implausible,
are still the facts ...

This is a weird but true story (with a moral) ...

  A complaint was received by the Pontiac Division of General Motors:

  "This is the second time I have written you, and I don't blame you
for not answering me, because I kind of sounded crazy, but it is a
fact that we have a tradition in our family of ice cream for dessert
after dinner each night. But the kind of ice cream varies so, every
night, after we've eaten, the whole family votes on which kind of ice
cream we should have and I drive down to the store to get it.  It's
also a fact that I recently purchased a new Pontiac and since then my
trips to the store have created a problem.  You see, every time I buy
vanilla ice cream, when I start back from the store my car won't
start.  If I get any other kind of ice cream, the car starts just
fine.  I want you to know I'm serious about this question, no matter
how silly it sounds: 'What is there about a Pontiac that makes it not
start when I get vanilla ice cream, and easy to start whenever I get
any other kind?'"

  The Pontiac President was understandably skeptical about the letter,
but sent an engineer to check it out anyway.  The latter was surprised
to be greeted by a successful, obviously well educated man in a fine
neighborhood.  He had arranged to meet the man just after dinner time,
so the two hopped into the car and drove to the ice cream store.  It
was vanilla ice cream that night and, sure enough, after they came
back to the car, it wouldn't start.

  The engineer returned for three more nights.  The first night, the
man got chocolate.  The car started.  The second night, he got
strawberry.  The car started.  The third night he ordered vanilla.
The car failed to start.

  Now the engineer, being a logical man, refused to believe that this
man's car was allergic to vanilla ice cream.  He arranged, therefore,
to continue his visits for as long as it took to solve the
problem. And toward this end he began to take notes: he jotted down
all sorts of data, time of day, type of gas used, time to drive back
and forth, etc.

  In a short time, he had a clue: the man took less time to buy
vanilla than any other flavor.  Why?  The answer was in the layout of
the store.

  Vanilla, being the most popular flavor, was in a separate case at
the front of the store for quick pickup. All the other flavors were
kept in the back of the store at a different counter where it took
considerably longer to find the flavor and get checked out.

  Now the question for the engineer was why the car wouldn't start
when it took less time.  Once time became the problem -- not the
vanilla ice cream -- the engineer quickly came up with the answer:
vapor lock. It was happening every night, but the extra time taken to
get the other flavors allowed the engine to cool down sufficiently to
start. When the man got vanilla, the engine was still too hot for the
vapor lock to dissipate.

  Moral of the story: even insane looking problems are sometimes real.

  (A better moral: chocolate ice cream cures vapor lock!)

Getting away from the religious references,  the point was a vapor lock
condition.

For the OP, scan your comp.  Any error codes?  Could be a faulty
pressure regulator, overheating condition, some other mechanical
problem that likely overheats or shut-off modes.