1997 Ford Expedition Engine Stalling - not idling after ign

My 1997 Ford Expedition has been stalling after ignition rather than idling when cold. I've had to drive around the neighborhood dropping it in and out of gear while riding the brake and gas pedals and eventually it will idle. I took it into a repair shop recently and they changed the alternator, replaced the serpentine belt and they thought that might help. I thought it was bad gas. My wife and kids just left to visit family and the car is acting up again. She will likely need to get it towed to a repair shop.

What should I have her ask them to look for? Is there a fuel valve of sorts or something electrical that is keeping it from idling. Other than that, it drives great. No hesitation in the engine.