I am relatively new to diesel tractors and am having an issue with a Kubota BX23 compact in the harsh weather in Michigan. My problem is this: Kubota has been sitting in the cold and snow. I started it up with no problems. Used it to plow the snow. About 30min. in to working my long driveway, the tractor started to lose rpms. The rpms dropped to about 600 and then reved back up to 2500. This occured continuously until I got the tractor moved to a spot where I could shut it down. I could only move the tractor when the rpms were up. This morning I checked the fluids and inspected for any leaks etc. None were found. I started it up after warming glowplug. It idled very well at 1200rpms. I let it sit for about 15min. with no problems. I decided to see if it would plow the rest of my drive. Another 30min of plowing went very well with no problems. Then it started acting up again. I moved it to my garage to let it completely thaw out. Could this be a fuel problem? What should my next steps be? Thanks for the help.