Droning rumbling sounds issues (1 Viewer)

[Wadepat2]

No expert on the matter but having no O2 sensors means it is an open loop system. In a closed loop system, the ECU gets immediate feedback from the O2 sensors to alter it's fuel maps and timing. In a open loop system, the ECU just does what it wants or is programmed to do. Tuning an open loop system will likely be more difficult to do.

However, you can't be the first person out there to do it. I think 2001+ GCC 100's went to closed loop system (w/ O2 sensors).

Thanks for mentioning it so I can plan ahead. Was thinking it would be plug and play . I was still planning to have tube checked but now will go that way from the start. There are plenty of tuner shops, superchargers and crazy twin Turbo Land Cruisers and Patrols here. Hoping to keep it as mild as possible and maintain some stockish relaibility. Plan to contact a tuner I have spoken to previously and see what's needed.

Checking parts site here confirmed 2001 GCC had the sensors. Mine doesn't. Even if they can tune open loop I'll get an O2 sensor/gauge to monitor.
Again thanks for pointing it out.

 

[Wadepat2]

Hi all, did some more checking and hoping someone else may have some thoughts before I start changing parts.

The vibration/droning seems to only happen in gear. Moving are sitting still both drones depending on rpm fluctuation. Also seems to do out more depending on the road type. Rough road more drone. In park or neutral. No drone.

Engine /Trans mounts?

Also found braces under headliner were no longer selaed in. Seam sealer is crusty and hard. Knocked most of it out and mostly fixed the metal clang from rear roof area. Maybe roof is flexing and causing vibration/droning through cab.

 

[Wadepat2]

Replaced engine and transmount.

Its actually worse but I did do some off-roading this weekend.
Also seems I can hear it booming randomly outside of car. Next step will be to change exhaust. Likely stock from cats back.

 

[Wadepat2]

New exhaust from cat back. Maybe helped a little but only enough to notice it haooens more from rough road and vibration. Supports between headliner and roof are unsealed and the black sealant is crumbling. Guess I'll start there next. Not so much an exhaust boom any more but more of a sound/resonance like being in a speaker.

 

[Jae]

I have been having the same issue. (My LC is 2000)
I replaced spark plugs and all mounts (engine and transmission) with OEM ones, fuel filter, fuel pressure regulator, and cleaned the throttle body. I don't have the engine cover. At Idle in N my LC is fine, but in the Drive, the rpm drops from 700 to 600 and I get an annoying deep bass resonance drone as well.

If you see the attached PDF, there are some suggestions.
I saw another suggestion in this forum that the rpm can be increased by adjusting TB setting, but I couldn't find it anymore.

If you find the solution, please keep us updated.

Did you give it a try from the manual? I attached the repair manual at #16.

 

[Wadepat2]

Did you give it a try from the manual? I attached the repair manual at #16.

Yep . Exhaust was really last thing to replace. Everything else on the doc was done or replaced from what I can see.

 

[Jae]

Yep . Exhaust was really last thing to replace. Everything else on the doc was done or replaced from what I can see.

I am having the same issue as the low frequency (resonance) booming issue. I would like to solve it out as well. I am having the issue only in Drive mode not P or N. It happens from idle to 70mph from time to time. At idle, it happens when the rpm drops from 700 to 600.

I thought the torque converter might be the issue. Before digging into the torque converter, I will give it a try for installing dampers first.


1. Did you add the Crossmember Damper Weight as well? I wonder it helps or not. Resonance can be changed by adding mass, but I checked the underbody, the body frame doesn't shake at all. The vibration comes out from the engine to the transmission, transfer case, exhaust. So, I was wondering the cross-member damper would work or not.

2. Did you test different exhaust pipe dampers? (32Hz, 34.6Hz, 39Hz, and 48Hz)
If I have the NVH tester, I may measure the accurate Hz and then I could install the right damper.

Because I bought a used LC three years ago, I don't know when my LC had started having this booming issue. I don't feel much vibration in the car, but the booming noise makes me crazy. I changed all mounts, exhaust headers, and one of the Cats. I took the engine cover off.

I hope the exhaust change solves your issue. Please keep us updated. I will also update when I try some.

 

[Wadepat2]

Exhaust helped booming at idle and drive but I still have a boom/resonance when driving on rough road or small bumps. All of my headliner supports are no longer glued to the roof. I can tap on roof from top and it sounds like metal to metal and crunchy adhesive. I'm thinking that big roof panel is flexing and causing the strange noise. It does it while moving and trans in neutral so it's not trans related for me. Definitely related to small bumps and rough road. Will be removing headliner and scraping all the old seam sealer out and adding new one this week. Issue has gotten worse the more off-roading I do. Even had black crusty seam sealer falling from headliner on some rough terrain. If it isn't the problem it will at least fix the roof flex and intermittent rattles.

I did buy a frame weight a year ago but it didn't help. My new exhaust has the damper also. Didn't fix the big problem but exhaust is super quite and smooth now without the weird boom at idle during rpm change.

 

[Wadepat2]

Finally removed the headliner. None of the support where connected to roof. 5 hours to remove it all, scrap all hard broken sealer out, reseal and add some foam tape hear and there. Drove home from the shop I use and it sounded much more solid. Still has some road noise/ vibration but sounds like I think it should for 22+ years old. Definitely worth fixing the flimsy rattle roof. Now if I could just fine the super loud squeak every time I slam door I would be super happy . Haha
Next step , timing belt and Supercharger.

 

[Jae]

Exhaust helped booming at idle and drive but I still have a boom/resonance when driving on rough road or small bumps. All of my headliner supports are no longer glued to the roof. I can tap on roof from top and it sounds like metal to metal and crunchy adhesive. I'm thinking that big roof panel is flexing and causing the strange noise. It does it while moving and trans in neutral so it's not trans related for me. Definitely related to small bumps and rough road. Will be removing headliner and scraping all the old seam sealer out and adding new one this week. Issue has gotten worse the more off-roading I do. Even had black crusty seam sealer falling from headliner on some rough terrain. If it isn't the problem it will at least fix the roof flex and intermittent rattles.

I did buy a frame weight a year ago but it didn't help. My new exhaust has the damper also. Didn't fix the big problem but exhaust is super quite and smooth now without the weird boom at idle during rpm change.

I am glad that you don't have a resonance at idle. I don't think the resonance on rough and small bumps comes from the exhaust.
I wonder you changed all exhaust systems including a resonator and muffler, or just a muffler? I am also planning to change a muffler, but I want to see whether it would solve the resonance issue.

 

[Wadepat2]

I am glad that you don't have a resonance at idle. I don't think the resonance on rough and small bumps comes from the exhaust.
I wonder you changed all exhaust systems including a resonator and muffler, or just a muffler? I am also planning to change a muffler, but I want to see whether it would solve the resonance issue.

Before exhaust I did have the boom resonance at idle. It's much better now. I changed muffler and resonator. Roof fixed almost completely eliminated the resonance while driving. I think I had multiple issues and the roof just magnified it.

 

[awesomeissquid]

Finally removed the headliner. None of the support where connected to roof. 5 hours to remove it all, scrap all hard broken sealer out, reseal and add some foam tape hear and there. Drove home from the shop I use and it sounded much more solid. Still has some road noise/ vibration but sounds like I think it should for 22+ years old. Definitely worth fixing the flimsy rattle roof. Now if I could just fine the super loud squeak every time I slam door I would be super happy . Haha
Next step , timing belt and Supercharger.

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I will be doing the roof supports later this month on mine. What did you find worked best for scraping the old stuff out and what did you use to replace it?

 

[Wadepat2]

I will be doing the roof supports later this month on mine. What did you find worked best for scraping the old stuff out and what did you use to replace it?

I used a flat metal paint scraper. It breaks up and came of pretty easy. Then I used plastic trim tool to add a little space and filled gap every where I could with a hi-temp adhesive I found at hardware store. It said can be used for metal to metal at super high temps. It also stays flexible. If I was home in US I probably would have ordered two tubes of automotive seam sealer. Foam around rear AC vents turned to dust when I touched it but I didn't have anything to replace it. Job all went smooth except for crazy stuck bolts on the handles right behind front seats. Had to chisel them until they moved then they came out by hand. Everything else was easy. Don't forget the rear seam all the way in the back. Tapping on roof quickly proved all of mine where no longer sealed to supports.

 

[awesomeissquid]

I used a flat metal paint scraper. It breaks up and came of pretty easy. Then I used plastic trim tool to add a little space and filled gap every where I could with a hi-temp adhesive I found at hardware store. It said can be used for metal to metal at super high temps. It also stays flexible. If I was home in US I probably would have ordered two tubes of automotive seam sealer. Foam around rear AC vents turned to dust when I touched it but I didn't have anything to replace it. Job all went smooth except for crazy stuck bolts on the handles right behind front seats. Had to chisel them until they moved then they came out by hand. Everything else was easy. Don't forget the rear seam all the way in the back. Tapping on roof quickly proved all of mine where no longer sealed to supports.

Awesome thanks for the quick reply! I will get some seam sealer on order.

 

[Wadepat2]

Droning and booming is mostly gone but still have rumbling suspension type noise which is similiar. Low speed and high speed. Seems rough asphalt is the worse. Maybe it's just old and I'll live with it. Everything is new and body bushings look good. Will check shock mounts today and see if I can find anything else.

Any suggestions I'm all ears?