Here's a recording of a strange and annoying noise I have in my 2002 LS430, 123k miles. Its a rattling clunky metallic sound that is most evident at higher speeds, when I'm just barely coasting, my foot has to barely be touching the throttle, not even enough to maintain speed. At lower speeds I can still hear it its just not as loud. Been noticeable for at least 4 months. I can make the noise happen so it is not random or intermittent. Car has NEVER thrown a CEL. In the video it is easily discernable in the first 20-30 seconds and also the last 15-20 seconds. Ignore the sound of the keys on my keyring bouncing around.

I've had the heat shields removed from the y-pipe and the pipe is ok. I've cleaned the MAF, the TB, the trans has been fully flushed with Amsoil, new WP, TB, pulleys, plugs, and transmisson mount. Engine runs well, no loss of power or sluggishness anywhere but I do sense a slight engine knock, not sure if its related. I have run a good fuel system cleaner though it several times recently. Several techs have looked at it and most can't tell what the problem is or shake their heads while saying one of the cats is probably bad. Somehow I doubt that. With the car running on the lift the noise can't be duplicated.

 

Sounds like one of your heat shields is loose, since the car has heat shields on the exhaust manifolds that are (somewhat) easily accessible, I would start there.

EDIT: does it do it with the car in park or neutral? or only in a driving gear?

 

He already mention he removed the heat shield.

 

From the y-pipe...not the headers or cats.

 

I'll have another look at the manifold shields, however with the car in park or neutral the noise does NOT occur. That's what leads me to believe its in the driveline.

 

It may not be, the drivetrain vibrates differently in gear than it does at idle. In park or neutral the engine is fre to idle with no resistance. That's why it builds revs faster than it would in gear. Put a load on the motor and the vibration frequency might just hit that sweet spot between the designated RPM's. I see this a lot.

Also, I am running through my head the things in the driveline that can rattle (only at certain RPM's you indicated) and NOT cause driveability issues...and I can't think of anything off hand. Torque Converter's sometimes rattle internally, but it causes a really crappy driving experience in the process, U-joints on driveshafts clunk but don't rattle, and If your rear diff is rattling at all, there are big problems .

All roads point to heat shield or something that's loose.

 

Put it on a lift and start tapping all the heat shield see if they are loose.

 

Turns out it was a bad driveshaft center support bearing.

 

Well after 18 months I still have this noise and its even worse now. It occurs all the time, even at idle I can hear it. It's quite noticeable when parked if I hold @2100 rpm, and it's really annoying at highway speeds. I thought it was the driveshaft center support bearing but it wasn't. That was a different noise. This noise seemed to fade a bit after changing the motor mounts 8 months ago but reappeared after a couple weeks. I had the car on a lift and thoroughly inspected everything, it sounds like the noise is internal and coming from within the bell housing area or rear of the motor. Any ideas? Y-pipe is new, cats are inspected and good, and resonator assembly is good too. Here's a better audio clip:

 

how do you know the cats are good? there could be a piece of the catalyst rattling around inside that you wouldn't necessarily be able to see unless you literally cut the cat apart...

not saying that is what it is, but it is something that is hard to eliminate, period...

 

I had the y-pipe replaced and at the same time we checked the insides of both cats, they look great. This noise is now to the point where it is constant, regardless of speed, but only really under little or no throttle, not under medium or heavy throttle.

 

Did you ever figure out this problem? My 02 LS430 is doing the same thing. Have not been able to figure it out. I thought it might be a tensioner pulley on the timing belt but I haven't had it checked out.

 

Hi! I have exactly the same noise. But in my case it is very low but the same. It happens when I leave the gas pedal at a normal highway speed. I think it is related to transmission...
Next week I'm doing a deep cleaning of the automatic transmission (with a specific machine) and an oil and filter replacement. If there is any change I'll tell you.
Any other idea?
Thank's.

 

After doing the auto transmission cleaning and the oil replacement (Toyota ATF T IV), the noise is no longer audible.




Transmission cleaning and ATF oil refilling process

 

:-(
Sorry to say that the noise was again audible ... Very very low but audible again... ¿? Any suggestion or idea???

However, the transmission is very smooth. :-)