I have a 2004 Stratus and while the engine has no problems in the winter/cold weather time. It does have 'issues' in the summer.
When the weather is warm, the engine takes a long time to start (5 s. or more) but this is only for after the car is parked (engine not running) for more than 2 or three hours. Also, the acceleration is not as good in the summer and the engine sounds 'irregular' when the car is not moving.

I have seen two car mechanics and both told me that I should have my spark plugs replaced, but those are fine (my car has only 36,000 miles on it).

Has anyone had similar problems or has any idea of what this could be or potentially lead to?

Thanks for any reply.