Bad engine rattle during decel
 

Hi all, new to the forum but not new to rotaries. I have a few build threads on rx7 club as FCinWV. Anyway

I am having an issue with my 05 where during decel dropping from 3 to 2k i hear a very loud metallic rattle. Ive searched and did some troubleshooting to no avail.

The car is catless. I then jammed the ssv actuator arm with a screwdriver to hold it shut, revd it, still made the sound. It doesnt matter if its under load or not. Ive tried to pinpoint the sound but the best i can get is passenger side of the engine somewhere. I found a video on youtube that makes the exact sound but there were no helpful comments. Thank you for any advice

Here is the link to the video

Update. I removed and blocked off the air pump system. Didnt help. It still pulls strong clear through the rpm range however I do have a hot start issue. Whether its related or not I dont know.

The only thing I can suggest is taking a stick of wood and applying one end to your ear and the other to various engine components. The one that is the source of the rattle will be heard loud and clear through the stick. That will help narrow down what is knocking.

Gonna play necromancer here... my car recently developed this same sound. A loud rattle matching the engine rpm when engine rpm is dropping with no load, clutch pressed, and closed throttle. Has anyone been able to diagnose this? Wishful thinking I'm hoping it's an eccentric shaft bearing and I'll be able to rebuild.
Here's a YouTube link of another 8 sounding exactly like mine: https://youtu.be/RLYjMO1s5Jw

Sounds like a harmonic issue where something is vibrating at a certain frequency (i.e., engine rpm). The engine loads the mounts differently during acceleration versus deceleration, and since the noise seems to be on the passenger side I suspect it is exhaust related. Did you remove the heat shields when you took out the cat? If not that is the first place I would look.

Does the noise stop if you release the clutch? If so > throwout bearing.

Does it with the clutch in or out.