First off, I searched but didn't find a thread describing the same symptoms my car has so I'm now posting for some help.

My TL has recently started to knock/pop on the front driver's side any time I accelerate or stop abruptly. I thought it was the brakes (they were at about 40% but I changed them anyway) but it still does the same thing. It's not the sway bar links, I replaced those a while back with the Moog ones. I was thinking it might be the lower ball joint. Has anybody here had similar problems?

 

I have had a few noises come from the front of my tl but with acceleration and during braking it does sound like it could be a ball joint our even the whole upper control arm. Only way to be sure is inspect the car. To date I have done ball joints, sway bar links and frame bushings, front, rear, and side motor mounts twice and a belt tensioner last week. Good luck, mine is quiet for now.