Double up throttle return springs!

Similar thing for me, except the throttle cable frayed. Low 12 second 70 Challenger heading for a busy intersection. Slammed on the brakes and went to shut off the engine....wheel became a little cocked and I spun around and ended up forward going up a curb into a little old ladies chain link fence. The cop that showed up was pissed but no one would say I was speeding. The lil old lady said it was such a shame something would happen to my "pretty" car and told the cop she didn't want to do anything. Feeling very grateful, after the car was towed I was back at here house and immediately repaired her fence.

My lesson, never buy a used throttle cable.