I have a unit that was donated and it seems to surge when you press on the accelerator until you push it down about 1/2 to 3/4 then the it runs just fine. when we first got it surged when you first started it and we replaced the throttle positioning sensor and it took care of the surge during start up but not when accelerating. just don't want to spend a lot of money replacing parts trying to fix it, it was donated. also is there away to slow the speed down to 5 mph? S# A910V Thanks