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Mysterious self healing car

why is it my car is fine when i take it to

the mechanic, but when I am on my mail route the car idles down and cuts off. It

even cut off while in motion a few times.

The mechanics say for the computer to tell

them what is wrong the car has to be doing what I say its doing for them to diagnose

the problem. What can I do to help diagnose

my problem? If I pad the accelerator while

it is in this mysterious shut down it stays

running. It shuts down before I can put it

in gear. desperately confused by mystery shutdown.

Make, model, year???

The mysterious self healing car is a 2000 Buick LeSabre with 130,000 miles powered by a 3.8 ltr V6.

jrh

My guess is a fuel delivery issue. Possibly fuel pump or regulator.
There may save been a recall on the fuel pressure regulator, if so see if the recall was performed.

My guess, especially if you’re in an ethanol state, is that you’re experiencing vapor lock. Doing all the drive-then-stop with a mail route gets everything really hot in the engine compartment, and if your fuel pressure is marginal from a weakening fuel pump or a partially plugged filter, even a newer fuel injected car can vapor-lock.

If you haven’t had the fuel filter changed lately, do it now. There’s a good chance that’ll resolve the issue.