Originally Posted by mark2gmtrans
This is something I have seen on a few boats and a ton of heavy machinery. It should probably have at one time had a spring on the throttle adjustment down on the fuel pump end of things that would help you feel it. It may still be there, but it probably is not all that springy anymore.
Basically all this is doing is starving the engine for fuel by completely shutting off the throttle to a setting where no fuel at all should be going to the engine. The little spring that may possibly have been there at one time a long time ago would just have been to kind of keep the throttle from going there on its own. Since the cables are usually stiff enough, I never worried about it.
What could be happening is that the whole mechanism is stiff enough that you can't feel the idle position, maybe combined with a weak spring. Consider lubricating everything in the throttle mechanism.