2002 Honda Accord RPM fluctuates

Hi. I have a honda accord 2002,180k miles. The rpm of the vehicle cannot remain on 1000 in idle mode. It always below 1k. If I attemp to on the ac the car starts to vibrate heavily and the rpm drops down to almost zero the it will go up again and continuous to fluctuate. If I manage to get the car moving the fluctuation stops but once I come to a stop, the rpm drops below one. Also the cars acceleration drop drastically with the ac on. The check light is also on as well as the abs and srs lights. It becomes worst when the temp starts to rise. And I hav noticed that the rpm fluctuation problem seizes at night when the temperature outside and that of the car is cool.I recently had my radiator changed to a bigger one but the problem continued.