2007 Silverado 3500. Starts cold well but has to warm up completely before putting in gear. If it isn’t warm the truck will stall and is very hard to start. Second problem is when in park idle is fine, when in gear and on a flat piece of road and foot off the gas it will idle at 1500. So I’m going about 40 km per hr. The truck sat for 6 months and worked perfectly before being parked.