Have you tried adjusting the stop for the throttle butterfly ( the piece that hits the small plate to stop the butterfly from closing )? ...mine had a small divot worn in it and about a quarter turn w/ a pair of pliers fixed the problem... what was happening is due to the divot in the plate it strikes the butterfly was closing too far causing the butterfly to be the cause of the sticking

.....just noticed you said sticking OPEN .... oops


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