That's what you pay mechanics to diagnose. There's dozens of things that can cause stalling. With no test results or observations to analyze, I can off a few suggestions but they're only guesses.
If power is lost gradually, as in a period of a few seconds, a plugged or collapsing pickup screen in the gas tank is a possibility. It will stretch out after the engine has been off for a few minutes and will allow gas to flow again for a few miles to perhaps 15 miles. Each time you'll get a shorter distance before it acts up again.
If the engine stalls instantly, just as though you turned off the ignition switch, it is typically related to a failing sensor. Those are monitored by the Engine Computer. It will set a diagnostic fault code that will tell your mechanic which circuit or system needs further diagnosis. There's well over a thousand potential fault codes. About half of them will also cause the Check Engine light to turn on. Having the codes read is always the place to start. Many auto parts stores will do that for you for free.
A failed diode in the generator can cause the battery to slowly run down and will cause the numerous computers to do weird things. That will be aggravated by turning on any high-current systems like heater fans, rear window defoggers, and head lights.
Thursday, February 20th, 2014 AT 4:56 PM