I've got a similar issue with my Lawn Boy # 10324. Something made a pop or click sound about 2 weeks ago when I was pulling the throttle lever towards me to slow the engine down as I prepared to empty out the grass collection bag, and the engine didn't slow down... engine stayed running at full speed. I took off the throttle control lever to see if the wire/cable itself had broken, but it hadn't. The cable had just slipped out of the little hold in the lever handle assemble inside the throttle control lever. I put the end of the wire/cable back into the hole and reassembled and re-mounted the throttle control lever on the side of the mower's handle.
So now, the choke position is still where it's always been with the level pushed all the way down away from me towards the engine where the lever is basically flat. Now, where you typically pull the lever back towards you just a little bit out of the "choke" position to where it's typically at a fast engine speed, the engine speed is now slow. As you continue to pull the lever back towards you where the engine should slow down, the engine speed gets faster. When you pull the lever entirely back towards you to where the engine speed is typically a very slow idle, it's almost like it's back in a "choke" position with extra smoke that's output from the muffler and the engine dies.
I don't really see many variations as to how the throttle wire/cable can be threaded back into the throttle lever assembly. To me it looks like it can only be threaded back in there the way I've got it threaded in there.
When I took the throttle lever off the first time after the pop/click I described earlier in this post occurred, a little black plastic piece fell out of the throttle lever assembly. I wonder if this little black plastic piece is related to the clicking sound that you usually hear as you move the throttle lever? It used to make a distinct/solid "click" sound especially when you moved the lever between choke/fast, but the lever, when moving it, is very quiet now.
Any thoughts/recommendations are greatly appreciated.
Thanks!