i have a new problem, only recently my car has been doing this: when i leave it off for more than 20mins, my car will sputter and sometimes stall right after it starts up for awhile. i think it could be related to the cold weather we´ve been having like maybe the gas freezing in the lines. so i got some antifreeze solution to put in my gas tank. it doesnt seem to be the problem. any suggestions. my car has never done this before in any other weather pattern.