Automatic Shutoff

The first two places I would look are at the fuel filter and the fuel pump. The filter will only cost a few bucks, so I'd go there first. The fuel pump will go between a hundred and a couple hundred.

I used to suffer EXACTLY the same symptoms on an 89 Regal. Was dangerous, because of loss of braking, etc.

The dammittohell dealership (it was in warranty) diddled with me for a couple of months, but claimed they could never make it happen while they had it. I offered to ride with one of their mechanics and show him what it was doing, but they always avoided that.

Finally, I contacted Buick with the story, and the fear that my family and I could be killed. They knew immediately what it was, and said there was a TSB on it.

There had been a series of bad electronic components in the ECM's which caused this to happen.

I would have thought your model was new enough to have avoided a bad run of ECM's but the symptoms are exactly the same.

At what point do you start to investigate the suggestions you already have gotten? If you are not skilled enough to follow-up on them, then you should be taking your car into a competent professional. No shame in that. Pay the money. It's part of owning and operating a car. If you are able to check them out, then what are you waiting for! Check them out, bring back your findings and you will likely get more information based on it.

If it just plain shuts off without warning, I wouldn't suspect pump/filter. Pump/filter problems I would think would have a little bit of warning via poor performance or even stuttering before it shuts off. I would say computer is shutting it down. Not necessarily any bad computer. Very well could be a crank position sensor or some other bad improperly working sensor. I'm not a mechanic though, so I could be way off.

Nope - not always, or even most times. For most drivers - who pay absolutely no attentions to their vehicle until it stops running, they wouldn't even notice if it ran a little rough for a while. But notwithstanding the unawareness of so many drivers, a fuel pump or filter can give no real notice and result in symptoms as described. In fact the classic "notice" of a dirty fuel filter is that the car will run, stop, run stop - after it's allowed to sit a while during the stops.

Or you could be right on. We all take educated stabs at this stuff sometimes - it's the nature of troubleshooting over a DSL connection instead of over the fender of the car.

Sometimes ignition modules become heat sensitive and will behave like this. You should have a stored code. You might wish to get it scanned.

I replaced my fuel filter but this has not solved the problem. I have checked my spark plugs and they are all good and the gaps are of the appropriate size. I am going to replace the ignition coil module and the PCM this weekend to see if that will make a difference. Thanks everyone.

I read through the responses and I didn't see anything that addressed this issue. The fact that you lose power brakes is concerning to me because you should have enough vacuum in the brake booster to provide for a couple (or more) of complete stops from expressway speeds. Unless you are pumping your brakes to stop once your engine dies you should not be losing power brakes. The fact that you do leads me to believe you have a vacuum leak in the brake booster or in one of many check valves that should be keeping the vacuum level up while you perform your emergency stop.

A vacuum leak won't make your car die on the freeway, but it's something to think about once you get the problem fixed.

Of course, if you have a hydraulic brake booster none of my concern is warranted.