Does the steering servo surge as well? Check that. That could be a key element in diagnosing your problem. If your steering servo surges as well, then go back and re-read C-Watkins post and inspect thoroughly.

If only the throttle servo is surging, and you’re confident the steering servo is fine, swap the two. Make the steering servo the throttle and vice versa. If the throttle servo still surges (what was the steering) I feel quite sure you have a receiver problem. But it is possible there’s a bad channel from the radio.

If you have a buddy that might temporarily loan you his receiver (that is the same or is compliant to your radio) try that. Or, if it’s different all together but is compatible with your current servos, borrow both his receiver and radio and go from there.

If you can’t get a buddies stuff for trial purposes, let us know. I’ll think of something else to try.