I’ve owned my 2004 Mazda RX-8 for about two years now never had an issue until now! Every time I start driving around 3k RPMS - 4,500k RPMS my car makes a (rotating grinding) noise but after 4,500k rpms the noise goes away. Not sure what is the cause I need help!! It’s a manual transmission.

 

The secondary shutter valve opens at about 3800 rpms. The valve is vacuum actuated, sits in the lower intake manifold and rotates to function.

 

Any engine codes?

 

currently no codes other than a misfire, but I’m going to take care of that. But the rotating noise is alil scary especially since I’ve never had an issue with this car before.

 

So what would be the problem? A vacuum leak? Or is it something worse. Sorry I’ve done some digging on yt but there’s really nothing and I honesty don’t know anything about rotary engines, but willing to learn and thank you so much for your help apex1 I appreciate everything!

 

Solve the misfire first. It could be related to that issue. The car should never be misfiring.