Has anyone considered that that might be a part of our "drive by wire" system?
There is no direct mechanical connection between our acceletator pedal and the throttle mechanism on our engine intake. It is done electronically, based on position sensors and other electronics and the movement is controlled by servos. These systems can produce noises.
My engine has done this since day one, and at 15,000 miles it performs flawlessly. I've tried to pinpoint the sound under the hood and really can't do so. It is clearly not engine pinging. Nor are any of the plugs loose or anything like that. I'm not sure, but I tend to think it is inherent in the drive by wire system. Given how well the truck works, I'm not inclined to worry about it, and certainly don't want a Nissan mechanic trying to trouble shoot it unless there is some reliable data out there that this is harmful.
Does anyone know how the drive by wire system works and whether it is the producer of this sound?