I've had a rattle coming from the passenger side of the interior of my car for the past 18 months. It seemed both temperature dependent (typically wouldn't be heard on the hottest days) as well as speed dependent (generally over 40 mph). Also, no difference with the window up or cracked open. I've done every rattle fix for this area I could find on Azine including:
-the under the passenger seat fix
-the outside upper door trim fix
-taking my B pillar trim off on the inside of the car and made sure nothing was rattling
- tightened up my door hinges and used Shin Etsu silicone grease on all the door seals (car has 80K miles on it, so I figured the seals might be not sealing as well

Anyway, despite doing all of these 'fixes', I still had an extremely annoying rattle in an otherwise perfectly running (and to me, great looking car despite age and mileage)

Fast forward to the present, just 3 days ago:
- I was trying to localize the rattle as best as I could- it sounded as if coming from the area of the front of the B pillar and back of the interior of the inner door panel. I removed the inner door panel (front passenger) according to these instructions (extremely easy and takes ~ 5 minutes):

https://acurazine.com/forums/3g-tl-2004-2008-93/how-remove-door-panel-687044/

I then had my interior door panel in the house, looking for any specific source of rattle- didn't note any. Then I went out to the car and started banging on the inside of the metal door (with the soft aspect of a fist) and noted a 'twang' near the back of the door when doing so. I called my brother in Colorado, and he mentioned that it might be the lock cable (that actuates the up/down button for the door lock) moving within either the door or in its receptacle (I have no pics, but here's the page from the shop manual- from Ron A's thread on interior door panel removal- look at the left panel and you can see the cable/ door button - it's in a white plastic 'cup'):



Moving along, I took out the screw holding the plastic cup to the door for the lock post but noted the plastic cup couldn't be separated from the cable. Not a problem as I used the fabric part of Velcro and cut a few small pieces to 'shim' the inside of the cup as without these, the cable is able to travel in the cup and make a rattle. I made sure that the cable could travel up and down without disrupting the velcro fabric.

I reassembled the door, was cautiously optimistic, and have been driving the car over the past few days (not too hot in NJ these days as to hide the rattle)- no rattle at all. My 18 month quest to rid myself of this annoyance after repeated frustrations almost drove me to look at a 2012 TL (well, not that seriously, but I did consider it).

I love my TL again. Now it's quiet like new, no rattles, and perfect again. I'm not a huge fan of the 'fix' of just turning up the stereo, and on occasion (especially in the early AM on the way to work) drive with no music on at all.

If you have a rattle you can't find and it's coming from the area as described above, this may be your fix (or you can hire the A Team and have them destroy your car- this is no dig against Acura, just a joke). I never considered having Acura look for this as I was pretty convinced they wouldn't find it, and charge me for looking.

I hope this helps.

 

nice job....now if someone can help me find the source of my rattle near glove box...that's been annoying me. only happens during hot days