Still trying to diagnose.... Research suggested alternator pulley with overrun clutch, ah wa! But upon double-checking mine (from 1997, manual) is solid pulley... so something else yet to be IDed.

By the way, do I have the right pulley? Did all manual cars since 1997 come with clutched pulleys or just later car from 2000ish?

Following this - I have the same issue on my 2000S. I rebuilt the motor and it started after rebuild - right around 2500 RPM. I have all new chains/guide rails/vario ramps. I have 5 months of winter to debug and figure it out, but not sure on where to even start!

The clutch in making the noise go away seems to be pointing to your throw out bearing or perhaps a rattle/vibration in the release arm or spring.

As an aside, I had all sorts of fits with shifting in 1st gear making horrible vibrations until I replaced the single front engine mount. It's a cheap fix easily done in your garage.

Thanks for sharing this pain, it seems not a serious issue with no performance degradation etc but it sure is bothering!

I take your input basically eliminating those components. I have no record of those valvetrain parts replaced, but several oil changes and filter gut-check in the last 15K miles yielded zero debris to suspect excessivel wear on them.

Let’s hope for the resolution soon!

Clutch feels good and no vibration/ rattle is felt through the pedal.

As mentioned earlier, I installed new 987 engine mount with new side pads too, so that may not be it... even though it seems as if I started noticing this noise after new mount and UDP installation.

When I replaced motor and transmission mounts, found that I experienced a couple of new types of sounds: 1) tighter motor/chasis meant more vibration transmitted to interior of car, making existing engine sounds more pronounced. 2) New sounds from things inside the cockpit vibrating more - at around the 2,500 rpm mark, under certain conditions I heard a new very pronounced buzz - that sounded like it came from engine. After some hunting I discovered it was the mesh hoop insert that vibrated very breifly. Decided to leave it as it adds some character! Hopefully you are experiencing something similar - more pronounced sounds resulting from tighter mounts.

Yes, it seems as if the new mount, together with UDP that drives the accessories at lower speed, promoted or exposed this noise.

My mesh inserts are secured with multiple zip ties (so I won’t lose them knowing how ridiculously expensive these plastics are), so probably my noise won’t be it, but will double-check. I’m pretty sure it comes behind the firewall, thought.

Keep ideas coming! With running out of ideas myself, I’m planning to drive the car with the serpentine belt off to see if I can positively rule out all accessories and pulleys.

My mesh thingies vibrate as well, definitely a distinct buzz.

Hi Boxstard,

The issue you describe sounds very similar to a noise I’m experiencing. I also have a 1997 2.5L.

Every time I ‘feather’ the throttle, either gradually on or off, I hear a distinct ‘chatter’. Full throttle / No throttle and the noise disappears. Most of the time I hear it when attempting to maintain a steady speed when cruising, but it's amplified at high RPM's when easing off the throttle after a hard acceleration (when joining a motorway for example).

Interestingly, unlike you - I can replicate the noise with the clutch fully depressed and the car stationary, by carefully holding the revs around 2,500 RPM and slowly feathering in a little more gas. Are you sure you can’t achieve this ?

I’ve just had my front engine mount changed (for unrelated reasons) which made no difference to the noise.

Did you ever find a root cause?

Keylime,

Perhaps the noise comes from within the muffler (loose shield) or failing cat..?

Good to hear you pointing to the Release Bearing. Bell Housing condensation will rust a release bearing over time and it will rattle. With the Engine running clutch out it will rattle when shutting the engine down. Clutch in no rattle when shutting down the engine. DMF I doubt it's the problem.

I noticed the same noise recently. The car is parked, but I had to move it so I drove it around the block. Very noticeable because I don't have the carpet over my engine cover, and my soft top is removed.

Still chasing the root cause... and I could not reproduce the noise with the car parked, clutch in or out, no matter how I tried with gentle throttle around the ‘sweet spot’ of 2,400 rpm.

FWIW-black silicone holds the mesh windscreens securely. Isolating that noise took a while!

Bump! Anyone with experience fixing this issue?