Why do the RPMs on my car "bounce" when I'm slowing down?

this could be a problem with your transmission. I've only seen this in one case and it was on a honda with a CVT "automatic ransmission". actually several cases on the same car. best way to see if this is an ongoing problem go to edmunds.com and put in the year, make, and model of your car and see if this is an ongoing problem. someone else may have the same problem and posted what was done to fix it. I would try to be better help but I cant really help you without knowing the year, make, model, and motor of the car.