my car seems to idle extremely high, the previous owner says it did this when he replaced some sensor, i didnt catch the name of it,as you can tell i know nothing about cars. also when you start or stop the car shakes. also I know I need to fix the last clamp thing that holds the muffler up so it squeaks when you go over bumps and actually it just seems to vibrate all time could this be My problem with my car shaking ? But what about this idling thing I was told by the previous owner that they could not adjust it . HELP PLEASE..