My Murray lawn mower idle oscillates up and down, I can see the spring
on the carb moving about 1.5".

I there a spring kit or some kind of throttle control that may fix
this this?

I rarely use this lawn mower and am about to put it up for sale, just
thought I'd fix this problem before advertsiing.

Its a Murray riding lawnmower, model 30552x12a w/a Tecumseh 10 HP

Thanks for any input..