I have a 1998 12V with about 80K on it. Runs great when warm, and starts good in the mornings. I live in the Northwest so plug it in at night most of the year. I notice when starting the engine when it hasn't been plugged in that the idle only hits about 550 to 600. Once it runs for a few seconds, I can give it some throttle and then the idle starts to pick up to the normal 700 or so. Is this a fuel preheater problem or something else?