And the saga continues.....
I have a 2001 RX300 purchased 5 years ago CPO. Had only 40K on it.
However, like you all observed, I did too get to experience the annoying vibration at idle, when in D.
The vibrations would worsen if I stepped on the brakes, putting a load on the system.
The vibration is annoying, but the low frequency hum associated with it drove me nuts, so much so that I literally *BLEEP*ed off Lexus Customer service. Well that is what they deserve for *BLEEP*ing a customer off. They had the same answers what everybody is getting..."Lexus has no fix for this". According to them, the engine mounts are great, they replaced the IAC valves, and also the passenger side engine mount. No difference.
Email after email, and some threats and suggestions later, I get this response in Jan 2007:
Any ways, what I suggested to Lexus it to do something to negate the bad hum (booming sound) associated with the vibration, and we finally decided to attach some weights to the exhaust system to be covered by Lexus if it helps even a bit or I will pay for the parts and labor. Here is an excerpt from the email communication I received after the call.
I was right on the money on that one. Don't know the cause of the vibration, which is still there, but the low level mind numbing hum associated with it is now gone.
So much for the "world class" engineers at Toyota.
Hope this helps a fellow out here.