1985 Chevy Truck I think something is wrong with the throttle cable?

[diono f]

I took my truck out today and got on the gas (floored) then when I let off the gas and went to stop the engine had high RPM's and I had to smash the brake to the floor because the truck would go 10mph on its own could it be something with the throttle cable?

 

[action]

Or the carburetor linkage, more likely.

 

[Chris D]

if its a 350 or 305 -4bbl the back Butterfly is probably slightly open . take off air filter with motor off look at