I have a 2000 ES 300 with 69,XXX miles on it. I 've been having problems for some time with a constant deep rhythmic chugging noise that seems to be coming from underneath the vehicle. The noise is most prominent whenever I am stopped in drive and especially whenever there are abrupt humidity changes or if temperatures outside are roughly less than 80F. However, I don't detect any of the noise or vibrations when I'm at speed. At it's worse the noise is accompanied by some vibrations that seem to course through the vehicle's frame in time with the chugging. Any idea what all this might be about? Thanks.

 

Whats the last major maintenance you have done recently?

 

Everything is pretty much up to date as far as I can tell. Oil change at 67,000. Tires changed, rotated and balanced and front brake pads replaced at that time as well. Air filter was also replaced.

 

I take it you haven't had it tuned yet?