Throttle gets stuck wide open in 3rd?

Sometimes when I'm driving in third the accelerator just shoots away from my foot, & down to the floor opening up my throttle in 3rd gear..

I hit the brake to avoid hitting the person in front of me, & try to pull the pedal back with my foot to no avail, eventually when I hold the brake long enough it snaps back to position but what the hell is going on?

Is the throttle cable breaking, or is the carb pulling itself wide open, & getting stuck? I really don't know what's going on!

Please help, this is a serious issue, & I've been fortunate enough that when it happens no one is too close in front or behind me...

I just don't want to find out what happens when there is...

Check your accelerator cable, and throttle linkage/return mechanism. Check your throttle return spring - especially if yours has an aftermarket Weber carb. The spring supplied with the Weber kit is notoriously WEAK.

Or could this be related to cruise control if the pedal really goes down by itself? Does yours have cruise?

Nope, no cruise control.

When it sticks, turn the key off without touching the accelerator. Then pull to the side of the road, open the hood, and have a look at the linkage.