When I accelerate to that sweet spot that the boost kicks in, my car sort of lifts and wobbles. If I don't hold the steering wheel and accelerate, my car will begin merging into the right lane. This isn't heavy acceleration, just enough to engage the supercharger, something like 2k RPM. When I let off the accelerator, the same thing happens in reverse. It settles and the steering corrects itself. The steering wheel never moves during all of this. But if I want to stay on the road I have to steer left by a pinky width or so. It had an alignment recently which didn't change the issue at all, and I get under it weekly, but I just don't know what could be causing this. If I had to guess, one of the tires is accelerating and the other isn't? Or, one of the tires is cocking sideways, despite everything being tight? And why does it lift?

 

I have stock suspension with 115K miles on it and it still tracks straight at any throttle input. Is your suspension stock?

 

motor mounts maybe ?

 

Did the alignment shop also align the rear of the car? The rear has to be aligned first and then the front wheels are aligned. Have the shop check for loose rear suspension bolts. Loose bolts will cause suspension to shift for and aft under acceleration and deceleration.

 

Also check the rear sway bar body mounts, these are known to break away from the body.

 

For the car to go right without any steering input 1 or 2 things are happening.
The left rear wheel is moving rearward or the right rear wheel is moving forward, or both are moving as said.
A bad toe link or 1 of the other lateral links in the rear suspension would cause this. Have your alignment shop have another look at it and tell them what it's doing.

 

The rear end has no alignment adjustments. You have to pony up for adjustable camber arms, rod ends, or eccentric bolts. The camber arm bushings are usually the first to fail.

 

How long have you had the car and did it always do this?
Was the car in an accident sometime?
How many miles on it?
Before the safety checks came into being here you sometimes would see a car going down the street crabwise, if those cars went through a puddle there would be four tire tracks coming out of the puddle.

 

I'm on a phone so I can't just scroll up and down, so here goes answers to all the questions: from memory.

The sway bar links are brand new installed by me today, from Ground Control--no difference . The backing plate for the bushings are bent slightly but not broken. The camber arms, toe links just got installed a few weeks ago by the same guy who did the alignment, from Ground Control. No difference before or after the install and subsequent alignment. The car has 35,000 miles and no accidents. The entire suspension, except the sway bar is aftermarket from Ground Control. Bushings looks fine on all the links.

 

This is the results from the alignment. The alignment was done on all four tires because I was replacing toe links and camber arms. I also had a constant tracking to the right before the alignment that wasn't fixed completely by the alignment. I talked to the guy and he offered to do it again but let me know hay he would be messing up a good alignment to fix the tracking because the tracking wasn't caused by the alignment but something else. I can't say one way or the other from these numbers.

 

Other than a bad tire or tires (even brand new) which can cause a constant pull, the ONLY thing that can cause a car to pull or travel (to the right in this case) is wheel alignment, there is no "something else".
If the alignment numbers are good (as they seem to be) the only components in the rear suspension that affect rear wheel steering would be a toe link or other lateral link that is moving under load because of a bad bushing or mounting hole on the frame end. The alignment is done with all these components at rest. The alignment is good at rest though under load something is moving then you have different alignment values which can steer the car abnormally.

 

What size tires are you running front and back? Mainly the rear.

 

toe-in is adjustable in the rear

 

The toe links in the rear are adjustable, and new. And I don't think that there are any bushings on the ground control toe link system. Rear tires are 285 width on a 19" wheel.

It appears all the obvious reasons for turning under load have been eliminated. What are less obvious reasons? Like, a control arm twisting because it has a bad bushing? Would that do it?

 

This is the ground control system, a picture from their website. I have basically an identical system on mine. All of the links have spherical bearings. So, there is no play and no bushings on any of the links. I could hang in the air from any one of these without feeling any give.

 

Thanks for the clarification. I guess I see your point. Under load the alignment is bad, but that doesn't really point to anything specific, except that a part is moving abnormally under load. None of the links have bushings any longer, it's all spherical ball bearings and most of those are brand new. Caster arms are old but as solid as everything else. What would I look for in a bad "mounting hole"? All I can see left to check is the control arm itself is flexing or bad bushing. Or the sway bar isn't doing anything and doesn't keep the tires even under load, allows them to point different directions. If my differential was goofed up, maybe one wheel would accelerate unevenly and push the car in a direction? I'm stretching beyond my experience here.

 

This is a guide to which part is what in my suspension.

 

I blame your rear tires and im only saying that because when I had 285's on the rear with stock suspension I had a shimmy in the rear. I'd step on it and the rear would dance/flop not breaking traction it was a shimmy. I thought it was the alignment or maybe the arms in the rear send were worn out I was at like 145k so it was possible in my case, yours with only 35k not likely.

Anyway, multiple alignments did not fix it and I started buying new arms to replace the ones in the rear. Well it was time to put some new tires on the rear so I did first before touching any of the arms in the back, I went back to stock size tire and my shimmy went away. I still have the full rear of arms sitting in my garage, have yet to put them on. I had on some same Conti Extreme All Seasons I have now just at 285 prior and it shimmy. Put some on at 255 size and it went away.

Just something for you to consider, hope you figure it out though. Best of luck.

 

Geez. That's an unexpected solution. Any idea what's causing the diffeeence?

 

I know you are getting a lot of input, mine included, though the solution will be simple when you find it. It’s not going to be rocket science it will be simple and logical compared to some of the proposed causes.
That said I can tell you what it won’t be: It won’t be anything to do with the sway bar because the sway bar does not and cannot affect alignment. You can test this by removing the sway bar link from 1 or both sides and evaluate.
It won’t be any particular tire size though it could be a single bad tire no matter what size that is. You can test this by switching the rear tires side to side and evaluate. Even the tires are directional it’s OK, you’re just doing this short term.

The issue will be something that affects the steering (toe in/toe out) of 1 or both rear wheels. You describe this as occurring under moderate throttle, does it act the same under heavy throttle?