It seems to be worse the hotter it gets outside. I took it in first to a dealer in Colorado Springs and they said it was water in the gas but it runs great pulling my big 9000 pound trailer up long grades, and runs great all the time. So a water problem... I doubt it greatly. Also you would think it would freeze up totally. I know how the mechanics are paid - if they put it on the computer and it doesn't show up, they only get paid one hour, and the dealers will say that its water, so you have to pay for it. I know a trained tech before he got a better job.