Just so I'm clear, the engine only stalls when you come to a stop and it will always restart, is that correct? If you mean it stops running while you're cruising at a steady speed, that's a different symptom.
You're right about losing its memory. A lot more is lost than minimum throttle, but that's the one you will notice until it is relearned. Short and long-term fuel trims are also lost. What is not lost from memory are the factory-pre-programmed fuel delivery values for every possible operating condition. As you drive, the computer starts with those values, then watches the readings from the oxygen sensor(s). Based on those readings, the computer will add or subtract a little fuel from the pre-programmed amount until it reaches the perfect mixture for every condition. That's the short-term fuel trim. When the computer sees the same modifications being made over and over, it uses those new updated values as the long-term fuel trim and will start running on those values immediately after startup. That results in lower emissions and better performance all the time. When the battery is disconnected or run dead, those fuel trims are lost, but normally they are relearned so quickly, you don't have time to notice a loss of performance.
On most cars, customer preferences that are programmed in to a computer are remembered when the battery is disconnected. Such things as speed-sensitive door locks turned on or off, a horn chirp when the doors are locked, and things like that are usually retained, but one notorious exception is with Volkswagens. They will not come out of park and the engine will not increase above idle until minimum throttle is relearned after the battery is disconnected or run dead. To do that requires the vehicle to be towed to the dealership when they are open. Typical repair bill for running the battery dead can run over $1000.00. Got'cha!
Wednesday, June 16th, 2010 AT 5:09 PM