MTD riding mower idles WAY too high. It was running fine last week when I put it away. It will run at this high idle but I'm afraid I might damage the engine or something. The cable seems OK it goes in and out like it should when I try to adjust idle only it stays very high. I am baffled??

Could be a gov. problem.
Check the butterfly on the carb and make sure its moving back and forward,

There should be a idle screw on the side of the carb (probably a flathead) its likely one of 3 screws - it will most likely be the one in the middle - that's your problem.
If you can't get it figured out let me know and ill try to help you out...