We have got a 97 grand prix that has been an excellent car until now. When starting it up-the idle is rough, right around 1000 rpm. Going down the road the rpm will continue to rise on its own and will not come down-creating the car to accelerate, creating a dangerous situation. When put in neutral it will rev very high. I dont think that the throttle is sticking, but thats what it acts like. Any suggestions. Thanks in advance.