1999 Honda Accord

I have had my accord for 3 years now and have only had minor cosmetic problems. Over a year ago though, I started having problems with the engine. When I was stopped, in neutral, or park the engine rev's itself as if my foot is on the gas as well. It has always passed service checks and inspections. It doesn't do it every time I drive, but it happens often. We have spent over $2000 trying to get everything under the hood fixed, and each time have been told that the problem won't continue, but it does. Usually, if I accelerate fast then it seems to go away. Someone that knows more about cars than I do told me that it seems like the gears stick, but other than that, I am stumped. Any idea about what could be causing this?