Sway on the Highway

[DrewFlu33]

Hi folks,

I've got a 2003 FX35 with ~88k miles, purchased with about 73k on it. Outer tie rods were changed by the dealer at my request before I bought it. Tires are Michelins with plenty of life left, inflated to 35 pounds all around.

Here's my issue: The car has developed a weird sway on the highway in the last 2k miles or so. This would be overstating the problem as it isn't that severe, but the best way I can come up with to describe it is that it's similar to driving a boat--it wants to float around in the lane as I get down the road. In most SUVs I wouldn't think much of it, but it's quite different from the precise handling I've come to expect from my FX.

I rotated tires recently and eyeballed my suspension components while I had the car up. From what I could tell, everything looked in order.

Any ideas?

 

[Dracula]

Shocks might be worn
Alignment
Worn suspension components
Do you have any vibration?

---------- Post added at 11:10 AM ---------- Previous post was at 11:08 AM ----------

Also did this happen right after the the tire rotation? if so it might be the tires

 

[DrewFlu33]

Thanks for the response! It was doing it before the rotation, which is actually what made me rotate the tires. Could an off-balance tire do this?

Shocks don't seem likely, as I'm not getting the signature extended "bounce" after going after bridge thresholds and the like.

It's not pulling to one side or the other, just sort of floating, so I don't think it's alignment.

Could it be a wheel bearing? I've noticed that "rumble strip" sound a couple times, but figured it to be the Minnesota roads that are freshly ravaged by an exceptionally harsh winter.

I haven't noticed a change in vibration--I sometimes get it through the steering wheel at highway speeds, but it's no worse than it has ever been.

I had a Subaru STi in a previous life and (long story) had a broken rear sway bar due to the ineptitude of a (dealership!!) mechanic changing out a wheel bearing. This reminds me of that a little, though a little more unnerving as the FX is more top-heavy.

What sort of suspension components has everyone had to replace? In doing my research before buying the car, I read about outer tie-rods, so I made sure to have those replaced before I bought it.

EDIT note: I do have the plastic guard that covers the oil pan off as I am planning to fabricate a "trap door" on it. I'm not sure when the problem started, but it well could've been the last time I changed my oil. Any chance this is the culprit?

 

[Dracula]

it might be just the tires and low psi. Usually when you have softer sidewalls, you might experience that. Does it com with stock 18s or sport 20s?
Also I would check on the shocks again, might be worn. Dont forget to have the alignment checked out as well, it sounds like it might be toed out

 

[wayne2ky]

man i'm having the same issue with my fx even after putting on new prada tire's.i'm going to get the car align hope that cures my floating issue:at-wits-end:

 

[la_fx35]

Shocks might be worn
Alignment
Worn suspension components
Do you have any vibration?

---------- Post added at 11:10 AM ---------- Previous post was at 11:08 AM ----------

Also did this happen right after the the tire rotation? if so it might be the tires

These are the area/parts I would start. How old are your tires? Do you have another set of tire to swap into and see if that makes any difference? Most of us change out shocks and struts around 60K due to the "boat float" ride quality. Now not to say that they are bad, but just worn that many of felt the difference in the ride quality comparison. You may also wanted to jack each tire up off the floor, grab the tire by the 3:00 & 9:00 position and rock it left and right to see if there plays. If there is it could be ball joint, tie rod end, or bearing problem.

 

[DrewFlu33]

It has the stock 18s--Not sure how old as they were on the car when I bought it, but easily more than 60% (probably 70%) of tread life left at this point. I will re-check air pressure tonight. Unfortunately, this is the only set I have.

Toed-out could be a good diagnosis, didn't really think of that when I was considering alignment. That would explain the random "pulling" in different directions.

I'm assuming shocks and struts are original on it, so that very well may be the issue. I suppose I'm struggling in wrapping my head around that; every vehicle I've been in that needed new shocks and struts has taken imperfections in the road very poorly (hopping "off-track" after going over a raised imperfection on the highway, extended "bouncing" over waves in the road and bridge thresholds, etc.) and I am experiencing none of these symptoms. The sudden onset of the issue seems to contradict the shocks/struts issue as well.

To be fair, I'm far from experienced as an FX owner and it could be that our cars just speak differently than others I've been around. I'm also really hoping to get some more mileage out of the beast before having to spring for such an expensive repair as well, poor PhD student and all! :D

I'll also jack it up tonight and rock on the wheels to see if there is any play. I did this to some extent when rotating tires, but I'll do it again to be sure as I was truly under the assumption that a rotation would fix the problem and quite possibly half-assed this check the first time through.

While searching these forums for a solution, I also came across the fix for steering wheel vibration--the tightening of a bolt on the rack. Is it possible that this bolt is loose and adding play to my steering and causing the issue? I haven't tried this fix yet, as I don't have a socket big enough to fit the bolt, but it may be worth looking into.

Thanks so much for all the tips and guidance!

 

[Dracula]

If you havent noticed already the FX has no rebound when you try to push each corner down to test the shocks.. Its a pretty firm suspension. Shocks arent going to cost a leg n arm. If you are mechanicallly inclined and have some basic tools, not counting spring compressor you could replace all 4 for about 260 bucks not counting $80 alignment after. The 18s soften up the ridr quit bit, compared to the 20s.
Yes tightening that bolt will help out a bit, you will feel a heavier steering feel (which is a win). But follow the guidelines carefully how to tighten it, you might end up damaging the rack.