my truck idols at about 3500 to 4000 rpm it seems like the throttle plate is getting stuck open. i have checked just about eerything else swaped the carb for another working one and the same thing happens. wondering how to get the throdle plate to lay flat. anybody?

 

is the linkage put together properly? i was having the same problem and i traced it back to a missing c clip on the throttle linkage