Yes, I have the exact same problem right now. I've identified it as a shot receiver. Except in my case it was the steering that was doing it when the engine revved. In your case, something has gone wrong on channel 2, and the interference caused by metal on metal while the engine is running, is leaking through the channel. Do you have another receiver you could try? That's how I finally identified it.

EDIT: Just a by the way, mine happened after a particularly hard landing from about 10 feet onto the roof of the car (upsaide down landing, no shocks on the roof [:@]), while trying to perform a backflip.