My car has been left in a cold garage for about 2-3 weeks without being driven. When it came time to drive the car, the engine was very rough and jumpy. It stutters at idle and is even worse when backing up, very jerky. Could this be a problem with condensation, water in gas tank? i have went to a local store to purchase STP Water Remover and poured it into my car after a full gas fill up. It seems to run smoother after a 10 minute drive, but it still jerks a bit and the engine light is still on. Would I have to wait a bit longer for all the water to be removed and the effect to be gone? thanks in advance.