Hijet Stalls While Cold

My 2005 Hijet will start up fine. But when coming to a stop (foot off the throttle) while the engine is still cold, it will stall! My mechanic thinks this could be a faulty sensor. When the engine has warmed up after a few miles there is no stalling. However, more recently when I come to restart after stalling while cold, I need to put my throttle pedal to the ground as if blowing away fuel from an old fashioned flooded carb. Any ideas please? Chris