Rough Idle on hot starts

Recently I've been having a problem where the car won't run on hot starts (the car starts and immediately shuts off). I've solved this by topping off the coolant and replacing the thermostat housing mounted fan switch. Now when I start the car after its been driven and parked for 15-30 minutes it starts to idle at 1,000 and then it drops and hovers around 600 rpm's. I've been recommended the main relay and fuel injector cleaners, but I've ran the injector cleaners and under inspection, the main relay looked fine. The car only does this on hot starts. On cold starts, it runs smoothly at 1,000 rpm.