An improved throttle valve assembly of the type which includes a throttle body provided with a throttle lever and a second, intermediate lever interconnected with each other by a roller/cam slot mechanism, said throttle lever being adapted to be moved by said second lever which is connected through the throttle linkage to the accelerator. The improvement comprises means disposed between the throttle lever and the second lever for adjusting the clearance existing between the cam slot and roller when the throttle valve is located in the vicinity of the idle position thereof, so that the excessive play that would otherwise arise at the accelerator when the throttle valve is in the idle position is reduced or avoided.