What has got into the throttle??..is it stuck at the carb, or back at the servo.....I'm not sure, but I got some battery acid and it LOCKED that sucker up at the carb......well anyways, I got some baking soda, and hot water, wiggled the throttle around and it came loose and haven't had a problem since........I don't think that's why it's getting stuck, but at least you'll know this if you happen to spill battery acid into the carb!!

Good Luck....