One problem related to engine funny noise has been reported for the 2010 Mazda CX9. The most recently reported issues are listed below.
I was driving my car when the transfer case on my 2010 Cx9 broke at 109. 000 miles and spline gear is worn out. Overwhelming oil smell coming back into car along with horrible grinding noise. Took to my Mazda dealer, Mazda wasn't sure if they could fix, suggested replacing transmission. Mazda tried to fix the transfer case issue, but could have humming noise. Instead of humming noise, after one day of receiving my car back, transmission is failing. Already put $2200 into this repair, but was told the transmission could fail at any time. I find this hard to believe after I put my car in for scheduled maintenance all the time and take great care of my car.