Just recently my Celica has started having problem. It started out that when my foot wasn't on the gas pedal my car was accelerating by its self up to 75mph. And then after I parked it and came back later and tried to start it when I turned the key and started the car the rpms went all the way up to 8000 and I had to shut it off. I didn't touch the gas pedal at all. What could it be?