I’m having an issue with my BX2380 throttle lever not holding an RPM. For example, when I mow the pasture, I’ll move the throttle lever to full RPM and as soon as I release the throttle lever the RPMs fall. I have to physically hold the throttle lever to maintain required ROMs. This happens at all RPMs. The tractor starts and holds correct PRM while at idle speed. Any suggestions? I hate to carry to the shop fir something I hope to be able to repair at home.