...starting after the engine is hot? The engine rotates but wont turn. When it cools down after 45 min-1 hr, then it starts with no problem. I've also had the check engine light on for quite a while with a P0420 OBD-II code (Catalyst System Efficiency Below Threshold (Bank 1) but I'm not sure that this is related to the problem of not starting when the engine is hot. I've also noticed that after driving on the highway, when i release the gas, the RPM fluctuates up and down for a short while then slowly drops off to normal. Is this related??