help - diagnose resonant noise when stopped at traffic light and gear engaged (1 Viewer)

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Wow, same issue. Once I hit 1,000 rpm the noise dissipates. If the idle is turned up would it solve this?
I wouldn't touch the idle of the engine to solve an idle boom.

Grab a measurement mic with an RTA (or find a friend with one, or get a subwoofer test cd) and find out what frequency the boom is.

Toyota made 5 different weights to cover 5 different frequencies from 32 hz up to 48 hz. Find your booming frequency, install weight, problem gone (or so that's the theory).

For the LX, the TSB is EG012-05. Not sure on the bulletin number for the LC.

I also suspect some high density sound deadening (dynamat, noico, etc...) of the floor or roof would solve this, too. There's a lot of flat, large steel panels on the 100.
 
So I found my problem guys! Maybe it's the same problem you are having. On my 98 LC It is the stupid plastic engine cover. I had my wife put the truck in Drive with her foot on the brake as I poked around. As soon as I push just a little on the driver's side of the cover, the humming/buzzing stops. I haven't decided if I will just take it off and leave it off or if there is something obvious like a rubber washer or something missing, but at least I know where the problem is now.
 
I have found a good cleaning of the throttle body, MAF and clean air filter help with the RPM going up ever so slightly and the drone disappears. I am currently having the drone noise but have not had time to go thru and clean everything up. YMMV
 
So I found my problem guys! Maybe it's the same problem you are having. On my 98 LC It is the stupid plastic engine cover. I had my wife put the truck in Drive with her foot on the brake as I poked around. As soon as I push just a little on the driver's side of the cover, the humming/buzzing stops. I haven't decided if I will just take it off and leave it off or if there is something obvious like a rubber washer or something missing, but at least I know where the problem is now.
Has the foam underneath disintegrated enough to not be functional anymore?

If so, join the club. My LX engine now sits naked up front due to this issue.
 

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