I have a Cat 330 engine in my motorhome, and it also automatically steps up to high idle (1200) for a few minutes, then back to normal idle. That is done by the ECU, and is normal. You can also manually increase your idle by bumping up the cruise control (accel) button, and cancel it either with the cruise control switch, or by tapping the brake. This, of course, while the coach is parked.
USAF 1965-1971; USCG Master
2002 Horizon 36LD - 2000 GMC Sierra 1500 4x4
Indian River, De