Sticking accelerator

[tvr5000]

Hi all,
Just wondered if anyone has experienced the accelerator sticking down on the tuscan? Had the box open and this seems to be fine. Also took the air filter box off and the accelerator always went back correctly. Checked for any rubbing marks on the box and none to be found. filter box back on, seems fine, start her up and in no time its sticking againg. You can pull the accelerator back and it returns to normal, but you have to manually do this with your foot.
Any ideas?