In my experience, its not the radio but something at the vehicle. Sounds like you are getting some sort of noise due to the engine running.

Does the problem happen at all when the engine isnt running?
Have you recently re-routed the antenna wire or trimmed it?
Is the antenna wire running next to any other wires?
Does the throttle channel glitch as well?

Check all your wires to make sure nothing is frayed/shorted.