Cold Engine Noise, need help diagnosing

[Burbman]

So looking for some feedback, wondering if anyone else has encountered this issue. Car is the 02 GTP coupe.

Cold start, engine fires right up and idles great. Quiet as a mouse. Accelerating away from the curb at minimal throttle, you get to about 2k RPMs with a light load on the engine, and I get a noise that sounds like a bunch of rocks being shook up in a plastic tupperware container. If you put your foot in it to get over 3k RPMs and increase the load on the engine, the noise goes away completely. As you decelerate and the engine passes back through that 2k RPM band, you again get the noise that sounds like rocks being shook up in a tupperware container. Once back at idle the noise is gone.

Definitely not a knock, but has more rattle to it than straight up lifter tick. Sounds like the piston slap I get on my 8.1L, but the 3.8 is not known for piston slap.

After driving about 2-3 mins, the noise disappears completely and the engine is smooth and quiet at all RPMs.

Cannot duplicate the noise in the driveway just by revving the engine, it has to be under part load while driving.

No noise at all on a hot start, once warmed up even a little there is no noise.

I've been doing a bunch of reading on this, and suspects include:

- Worn Harmonic Balancer
- Lifter noise caused by oil drainback over night
- Worn Supercharger coupler
- Incorrectly installed flex plate cover

Right now running Mobil 1 5W30, about 4k miles on the oil, and I forget what kind of filter, probably a Napa Gold.

Anybody have anything similar?

[hockeybawler]

My guess would be a worn supercharger coupler

[Scottydoggs]

could be a worn out pulley. id start with taking the sc belt off and drive it.

you can drive for a short time with the other belt off as a quick test (like down the block and back) if you cant find a bad pulley hand spinning them.

[Burbman]

Good idea, thanks Scotty!

[Burbman]

Update: Took off the SC snout and changed the coupler and oil. Reassembled and now the noise is louder.

Here is what it sounds like at idle: YouTube.

Also now it idles like sh!t and is setting a P0171 code, bank 1 lean. If I take off the SC belt the noise goes away and it idles fine. Is the SC toast?
The vacuum fitting under the snout was all dry rotted so I changed that.

[Scottydoggs]

if it goes away sc belt off the sc is likely has bad bearings.

[Burbman]

Are these rebuildable with new bearings? Best course of action?

[Scottydoggs]

you can buy a bearing kit, but in the end its less work to buy a used blower.

[Burbman]

Problem solved: Ordered a rebuilt unit from PSE Superchargers. Fully remanufactured, they will install the 3.4 pulley for me and I also had it ported/polished as well. Wasn't cheap but should fix the problem.