ok i have a 96 integra LS and im having problems with my AC. and was wondering if i can get some inputs below is a list of whats happeneing. this is all when my AC is on

- AC is not cold at all (put added free on) still not cold
- engine bay makes a knocking noise and feels like the car is going to stall (drops down to about 200 rpms) , but it doesnt
- while driving, about every 15-20 secs i hear the knock and my car lags a bit, then anohter knock and it goes back to normal. its like mashing on the gas, letting og and mashing on it again

this does NOT happen when my AC is not on. any suggestions?