Hey guys I've been fighting a this issue for a couple of years now finally got fed up and did a complete front end overhaul this week. I've been experiencing EXCESSIVE bump steer when going over bumps, cracks, and small dimples/potholes at all speeds. It's really bad and will throw my car into the other lane if im not holding the wheel firmly I always have to correct the wheel to get it back in lane. I'm surprised I've haven't been thrown into a guardrail yet because that's how bad it is. My first thought was tires, got new Hankook V2 concepts but that didnt solve the problem, then switched over to Blizzacks for the winter but no dice. Finally with 165k on my 03 TL-S i decided to do a complete front end overhaul I just finished replacing:

Complete Tie Rod ends (Moog)
2x Lower balljoints (555)
2x Upper Control Arms (Doorman)
4x sway bar link and bushings (Moog)
Radius Rod bushing aka strut mount bushings
2x lower control arm bushings.
4X KYB Excel-G with all new strut mounts
and then finally ended it with an alignment.

The alignment shop said everything was tight and they were able to align it perfectly, I mentioned my bump steer but they could not pin point where the problem was. The tech took the car for a test run and noticed the issue he said it could maybe be related to the rack and pinion. Could that be the source of my issue??

 

If you're doing all of that, I would just pay a mech to diagnose it. I don't think they would charge you a diagnosis fee for "Maybe it's the rack and pinion."

Issue definitely seems to be in the steering. Does it happen more if the bump is under the left wheel, or the right wheel? What happens if you go over a speed bump with both wheels?

 

Sounds like there is Low Pressure on the Rack...
Perhaps Power Steering Pump too?

 

Steering feels tight as new, turns nicely no soft spots or anything. I don't have any whine or anything coming from the pump. Going over speed bumps at low speeds is fine car stays straight. Although at 35mph+ the car will just choose wherever it wants to go when there is an imperfection on the road it usually followed the crown slope of the road and just pulls that way. I'd have to correct the steering wheel and bring it back to center.

Driving on the interstate is fine no issues when there is no crown on the road car stays straight as an arrow. It's too bad I love this damn car so much I keep throwing money at it!

 

did you find out what it was

 

Amusing - not because of the necropost, or the lack of capitalization and punctuation, but because one only needs a momentary glance at the OP's profile pic to know what the problem was.

Since you're asking, I'm guessing you have bump steer.

Which of course begs the question... is your suspension lowered?