Have a 2001 Olds Alero Sedan, GLS, 3400, with 114,000 miles. Bought it used in October 2012 from a local GM Dealer. Have had no problems or issues until late April 2013 when the thing just shut off going down the road. Pulled off to the side, put it in Park, cranked it over, and it took right off - thought it was weird! About a week later, same thing happened, but this time I noticed the Tach went crazy, some hesitation in the engine, and then shut off. It has done this now close to a dozen times, sine late April, and thought it may need a tune-up! Replaced air filter, spark plugs, fuel filter, and cleaned out the throttle bottle in mid May 2013, as the wires, and forward O2 sensor appear to have been replaced prior to this. It ran great for about a week, now it's back to its old tricks! If I noticed one thing, it seems to do it more often on warm or hot days, especially with the A/C kicked on. Almost acts as if it's got a mnd of its own, and saying, "OK, I need a little breather here as I'm hot and just need a break for moment!" Since it seems to be fine in cold, cool, or warm weather, but acts up on hotter days, I'm wondering if it could be the 'Crankshaft Sensor'? Of course, it could be a number of issues, but seeing as I get 'NO' Check Engine or Service Engine light, or any other indicators for that matter, and it's start right back up with no problem, I just wondered if on those hot days it doesn't know what to do with the build-up of heat under the hood, or in the engine, and the electronic system is telling it to shut down as a safety precaution? Scratching my head on this one! Thanks for any help, Al D.