When I start my after it's been off for a while (over an hour at least) it idles at almost 2500 rpm. If I let it sit, it takes a long time to slow down. If I drive for a few minutes, it gradually slows down to around 1500 rpm, and after maybe ten minutes, to the normal 750 rpm. For the first few minutes, the car actually idles fast enough to pull the car without touching the gas pedal! I have to keep a foot on the brake when backing out of a parking space. Does anyone know what could be causing this? It's been doing this for a long time now. Also, the outside temperature doesn't affect it; this happened during the summer as well.