Possible causes of a car idling high while in park include the car having a bad accelerator, an overheating engine, the fuel pressure regulator operating at low pressure and the alternator acting up. One symptom of the car's idling problem is the driver having to apply brakes intensely when parked.
Each of these possible causes has an easy solution. The accelerator and alternator can be replaced if they are diagnosed as malfunctioning. The overheating engine can be repaired, though a certified mechanic will need to check the cooling system. The fuel pressure regulator can be examined with a fuel pressure gauge and replaced by a mechanic as needed.