Hey everyone I don't know a whole lot about cars to be honest, but I have a 92 accord two door EX 5-speed that has been making a racing sound when parked or sitting at a stop light.

Basically the RPM's jump from say 1500 to 2000RPM's and back down again over and over. It only started doing this about 4 months ago. It's never stalled or anything like that but it does kind of scare me since it doesn't sound very healthy.

What could this be?
Thanks