Chrysler Repair: 99 Concorde 3.2L engine dies on highway, spark plug gap, engine controller

Question
My 99 concorde (3.2L) will die if I am going over 70mph or running the a/c.  Took it to two dealers and they could not find a problem.  Any thoughts as to what the culprit might be?

Answer
Hi Shane,
If it can't be evaluated at the shop then yo have to be ready to check for the reason when it happens. Basically there has to spark and fuel (at the correct mixture with air) to have ingnition and power. So I would suggest you carry a spare spark plug and ideally have a friend aboard when you next need to go on the highway, or want to try to cause it to occur again. When it dies, if it won't restart for awhile then that is the time to put the spare plug into one of the spark plug connectors, and while holding  that connector, place the threaded body of the plug against the cylinder head while the friend cranks the engine. Observe for a good quality spark to jump the spark plug gap or not. Also, listen, when you first turn the key to run but before you try to start it, for the sound of the fuel pump humming from the rear underside of the car which lasts for about 1 second. Then again when the car dies and won't start see whether that humming is or isn't present. Those two tests will help lead to the cause.
I trust that the dealers did a fault code readout on the engine controller memory. If not, then that would be a good thing to now as it may give a clue as to why the shutdown. You didn't say if the car starts right away after it dies or does it take a few minutes of cooling down? If the latter then I would suspect one of the two timing sensors to be breaking down due to heat, then recovering as it cools down.
So let me know what you learn from trying any of these suggestions.
Roland