My 2001 expedition 93,000 miles is hard to start every morning and if i let it sit for 8 to 10 hours its hard to start. If I let it sit for 2, 3, or 4 days a huge plume of white sweet smelling smoke comes out and it is real hard to start. after starting it runs great no smoke comes out while driving does this sound like a cracked head, cracked block or bad head gasket. I have already had the valve stem seals replaced under warranty at the ford dealer ship. Any thoughts or suggestions would be apreciated