After running my automatic '04 Lancer LS for more than half hour or so, especially if idling a lot, the idle RPMs get higher and higher until they're around 1.5. While stopped I have to hold the break pretty hard to keep from moving. If I shift to neutral or Park, the engine races to between 2-3000 RPMs. Then it shifts rough too. If I turn off the car for about 10-15 minutes, idling RPMs drop to normal; under 1000. What could the problem be?