Have a 03 Sable that keeps dying on us. Does not happen in the winter, only in warm weather. The car has 56K miles. Has been to the dealer many times with no luck. They have replaced fuel filter, flushed the fuel system, cleaned injectors, replaced the #1 c02 ox sensor (the one at the top of cat) and replaced fuel pump nothing seems to help. Gave up on taking it back to them. This has been going on for about 26K miles. Things that happen before it quits is the Speedo shoots up, it will spit and sputter; the dash lights will go bright and dim and then die. Sometimes it will not restart unless we let it sit for awhile. Sometimes when it dies nothing electrical will work i.e. radio, windows, fan etc. Headlights will work but will be dim. I have checked what ground connections I could find and they were all tight. The battery is 2 years old and is good. It cranks just fine. There is plenty of power when it is running. Could this be an ignition switch issue? Anyone one have any suggestion?

 

Has the battery been replaced?

if not, I'd wager is a battery dropping a cell when it gets warm. I had the same issue on a small Cadillac I was driving for a while. Replaced the battery and it was all good after that.

it could also be the voltage regulator wigging out (which I'm leaning towards actually). Since it's a heat related issue that affects all electronics I would check those two first.