So for quite a while now, my Altima has had this rough idling sound. I was under the impression that maybe that’s how it’s going to sound once I start to get up passed 100,000 miles. Then I thought maybe it was the Mass Air Flow sensor that may be dirty. I cleaned the MAF, sound didn’t go away. Listening closely, it sounds like the noise is the loudest by the alternator. Many videos on YouTube later, none of them sound anything like mine. It does it when the heat is on or off, and then goes away when I engage the a/c. Anyone have any other suggestions? I’d really appreciate the help. I don’t wanna replace the alternator unless I know for a fact that that’s the issue.