Most of the imports have very little room for error in charge quantity. A typical amerinca AC might use 3 12 oz cans of R134, while a Honda needs something like 20oz (depending on model, this is an Accord V6). An over-charge can damage the compressor, and also will make it run poorly as it is very hard to move liquid R134a through the compressor.
Best bet is to have it discharged, evacuated, and charged using a weight scale so that the charge is dead on. If you put in a whole 12oz can, chances are it was then grossly overcharged, where at the beginning it was probably under-charged due to a small leak somewhere...
probably will cost about a hundred bucks to get that done, plus the cost of the freon...