Rumble/Hum at Idle

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KY Tundra

KY Tundra

10 Year
Joined
Feb 8, 2015
Threads
28
Messages
144
Location
Louisville
I've noticed over the last few weeks a low frequency "hum" when sitting at idle in Drive. Tach says 600 RPM. If I shift to neutral, tach bumps up a bit and the noise goes away. It's one of those noises that is hard to describe, almost like the pressure imbalance if you have one back window open. Everything else sounds normal at any other speed, RPM. Stock exhaust. Anyone else had this issue?
 
Remove the plastic engine cover and see if it stops. It's very common for this piece to set up a harmonic vibration at low idle. If that's the problem you can repack the noise insulating foam on the bottom of the cover or fit some rubber grommets on the 4x mounting points, or leave it off.
 
Mine does this with or without the cover. I've learned to live with it but I'm about 99% certain its harmonics due to the exhaust. My muffler even has a huge weight/rubber thing attached to it to reduce the harmonics. I think the only likely fix is to replace the exhaust with something aftermarket.
 
Probably a stupid question but did the PO remove the resonator? I removed mine a months or so ago and it has a very nice (imho) low rumble at idle.
 
Ramathorn15 said:
Mine does this with or without the cover. I've learned to live with it but I'm about 99% certain its harmonics due to the exhaust. My muffler even has a huge weight/rubber thing attached to it to reduce the harmonics. I think the only likely fix is to replace the exhaust with something aftermarket.
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I have an aftermarket exhaust and still expereince the vibration at idle. Or "booming" as some reference it.
 
I don't think the PO owner modified exhaust. Sounds pretty stock. And this isn't a nice, low end V8 rumble, it's an annoying, hurt your ears, droning. Is 600 RPM correct for idle in Drive?
 
KY Tundra said:
I don't think the PO owner modified exhaust. Sounds pretty stock. And this isn't a nice, low end V8 rumble, it's an annoying, hurt your ears, droning. Is 600 RPM correct for idle in Drive?
Click to expand...
It's a little low, as is mine, and is due to multiple factors: dirty throttle body, injectors, or just a gummed up system. There's really no telling, just a number of things you can do to get your engine running back to normal spec.

Sea foam and 44k gas treatment is a good start, but I'd go deeper and clean the throttle body and butterfly valve. I'm pretty sure a coil pack that is on its way out will hurt idle performance as well. I'm also going to be replacing my engine/transmission mounts soon because while they aren't the cause of the vibration, they are 17 years old and are probably brittle like every other rubber part on my LX.
 
Anyone figure this out? I feel like after I changed my T case fluid this was better for a while but now the drone is back at idle but subsides in neutral
 
Have you check your catalytic converter shields? I found mine all 4 clamps had rusted off and that shields would start rattling at this resonance frequency at very low /idling rpms.

Craw under the truck and use a rubber mallet to gently tap these shields to see if they are loose. I used 2 sets of stainless steel hose clamps to tightened them back down and it has gone away.

Also the plastic intake manifold has a rubber bushing that cracks with age. If you ever do your sparkplugs, you have to remove this (it connects to the engine filter and throttle body) and you can replace that bushing if it's cracked.
 
I have the same thing in my 2004 (deep bass sound in D at idle). I'm pretty sure it's the exhaust getting into resonance. I believe there was even a service bulletin describing to the techs how to add different weights to different parts of the exhaust system to cancel the vibrations.
Also, I feel like it got a little louder after I put my rock sliders on but I'm not certain. I didn't have the truck stock for very long when I first bought it.
 
dogdaysindurham said:
Have you check your catalytic converter shields? I found mine all 4 clamps had rusted off and that shields would start rattling at this resonance frequency at very low /idling rpms.

Craw under the truck and use a rubber mallet to gently tap these shields to see if they are loose. I used 2 sets of stainless steel hose clamps to tightened them back down and it has gone away.

Also the plastic intake manifold has a rubber bushing that cracks with age. If you ever do your sparkplugs, you have to remove this (it connects to the engine filter and throttle body) and you can replace that bushing if it's cracked.
Click to expand...
It's not a rattling like the shields would be, it's more of a bass sound.
 
I always feel like there is too much drive and it loads everything up to much when I leave it in drive with my foot on the brake. I just put it down to being a v8 with lots of torque. My 3.0 subaru didn't feel anything like this, but that seemed to have to much drive under braking and coming to a stop, If that makes sense. I just pop it in neutral as it feels that if I slip my foot of the brakes by mistake in traffic then it would trash the cars in front like a Monster Truck.
 
I also have the booming drone sound at 600rpm. Drives me nuts. No engine cover and exhaust shields are tight.
 
Same here... Correct me if I’m wrong but it didn’t used to be like this, I’ve had it since new and mine started at about 270k miles.
 
Check out TSB "Exhaust Booming at Idle"

It mentions various 32Hz thru 48Hz Dampers to filter out the low frequencies.
In addition various bolts to tighten on the Catalytic Converters and Exhaust parts,
Engine Mount insulator and a left hand side weight.

Factory warantee coverage unfortunately is only 72 months.

I wonder if most of the annoyance can be removed with some home-made dampers
that mount on the rear of the main muffler????
 

Attachments

I'm guessing that those dampers on the rear of the main muffler will get rid of most
of the noise. I wonder if we can find a vehicle that has had this TSB done on theirs that we can get a picture of? Maybe someone has a parts car?

EDIT: After posting this I found a photo I had of the undercarriage of my 2002 LX470. This shows one of the Dampers on the end of the main muffler:

201712-033.webp
 
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