ORIGINAL: JPMacG
The first thing I would try is replacing the throttle servo. There may be a vibration related problem within the servo. I have had similar problems that I traced down to a bad connection on the servo circuit board.
If the problem persists with a different servo, then you may need to send your receiver and transmitter in for check out and repair.
I have an extra servo and reciever and might give that a try. I somehow dont think its a vibration issue.
Thanks