I parked my car about 2 days ago and couldn't drive it due to bad road conditions. It got down to 15 degrees here. The roads cleared but it still remained cold. I started it and it warmed up fine. When it got to normalboperating temp I was waiting for the windows yo defrost and it started idling really low. I tried to give it gas and that seemed to choke it because it would just die instead of rev up. After that it continued doing the same thing. It would idle for a bit then die or I step on the gas and it would die. There's a tad less than a quarter tank of gas in it. Could the gas have frozen at 15 degrees or could there be another problem?