2002 Neon - car idle rough with the A/C on. Have changed spark plugs, air filter, etc. and still runs rough. Took it to a shop and there are no fault codes. The problem only happens when the car sits in the sun for a few hours (hot) and will only happen when you come to a stop. The idle normally runs at 750rpm (No a/c on) and will drop down below 500 intermittently with the A/C on). Should the idle increase when the A/C is turned on with more load on the engine? If so; the idle remains at 750rpm. Any ideas?