My car refuses to start under certain conditions. On a cold day, then it fires up but if it is hot or raining then the engine just winds away on the starter. Fresh plugs, fuel injector cleaner, nothing works on fixing this problem.

My 1999 Cavalier turns over for a long time before starting(50% of the time). this problem wont happen when others are around but my obd 2 says the timing, O2 sensor readings, and idle rpm all change constantly while idling. its all one stupid thing im guessing