Rep Power: 0

I have a 1999 CIVIC DX, and recently a friend of mine decided to help me add refrigerant to my A/C because it wasn't getting cold enough. So while he was adding the refrigerant, instruction said to turn the car on with A/C on highest. While the refrigerant was filling, all the sudden there was a loud PSSSSSH sound, and we looked under the car, and there was a greasy mist on the ground. The a/c no longer gets cold and it tries to make a pssssh sound until there was nothing to spit out. My car's RPM now drops really low almost to 0 when I turn the A/C on for about a second, then raises back up to normal and drops again and keeps repeating(I dont think it ever happened before), and it only happens when the A/C is on.

Does anyone know how to fix this problem?
Please help out and thanks!

 
Rep Power: 518

I'd guess it's now way overcharged and you should take it to a professional to have the freon recovered from the system then recharged with the correct amount by weight, then see if it works right and diagnose it properly if it does not. The high pressure safety relief valve should probably be replaced to ensure correct operation too.

 
Rep Power: 0

Sorry late reply, I had a private mechanic recharge it and the a/c works fine but after a midway drive home, the engine rpm started to fluctuate when on drive and on idle when the a/c is on. The a/c works, but sometimes it blows just fan air(every 3 minute ish). Any idea? I don't want to take it to a professional mechanic because I'm going to sell this car soon.

 
Rep Power: 518

What's the difference here?
Sounds like it is cycling the compressor on and off (normal) and you feel the temperature rise several degrees (and all that humidity from outside) while the compressor is cycled off.

Use "recirculate" to reduce the inrush of humid air?