I couldn't believe it! I pulled my Ryobi 4040 apart and checked the cable for the throttle back to the trigger in the handle several times. Finally, I discovered that it was the screw at the top by the trigger, which was too tight (But this was happening before I took it apart for the first time!). As soon as I loosened that screw, the trigger released properly after staring it up, rather than going full throttle, like the missus out of control. It idled properly after that. It might just need a thin spacer between the handle sides or casings to just tighten it enough, so as not to lose the screw.
Terry in SE Queensland., February 2020
