I second that, and after you get the 74mm in your hand, If you are brave, you can remove the 4 or 5 clips that hold the plastic cover and look inside.
What you will find is a motor, 3 sets of nylon gears and a big return spring.
Push the throttle plate wide open and let it go - the spring should return it to idle position pretty fast.
If not - lube up the nylon gears with white lithium grease and try again.
If it still sticking, then deal with the source where you bought it for an exchange,
YOU DO NOT WANT TO TRY TO REMOVE THE THROTTLE PLATE AND SHAFT.
( Although the experts do when they bore one out )