When car is in park or stopped the rpms fluctuate below 1 and car stalls out.

Idle speed is normally controlled by the idle air control motor. These units get dirty and fail, but can often be cleaned and restored to normal function. You will need to remove the unit to clean it, but be careful not to damage the plunger and seat. Use carb + choke cleaner and maybe a small screwdriver (carefully), then blow unit out with compressed air. Replace gaskets as needed. Also low idle can be caused by vacuum leaks, bad O2 sensor, clogged exhaust (cat converter), dirty MAF, bad coolant temp sensor.