My idle is at like 2100 when i start the car cold.. it used to be about 1600

my car has erratic idle when the engine is warmed up.. however when i turn on AC, the erracticness seems to be gone.

Any idea as to what the problem is? I know it can be a number of things.. but just wanted to hear some more thoughts

 

I have the opposite problem. It starts up high, then drops to almost nothing.