My Qx60 is 3 yrs old and hardscrabble sound under the vehicle like a cover is loose, but we can't find anything loose. The engine recently started revving high when I start driving. It revs up to 3 and stays there for about 10 to 15 seconds before going down to 2. Does anyone know what that sounds like. I must say , I wish I hadn't bought this SUV. Problems since I bought it.