2007 Mule 610 with about 160 hours. I noticed it last winter and it's back again. This is typical; 20 degrees outside, it starts OK in the unheated garage and after just a little running idles and runs ok w/o choke. Ride it say for 5-10 minutes at 1/2 throttle across the snowy field but when I stop it won't idle it just stalls. It starts right up and will idle roughly with a little extra throttle but still won't idle on its own. Plug is good (was changed at 120 hours along with valves set) Gasoline is kept fresh, removing gas cap doesn't help. Didn't used to do this until last winter. Once spring arrived it was fine again until this winter so it *must* be temp related. I'm not sure where to look, any thoughts? TIA.