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Car shimmy, after an hour

I have a 2006 Hyandai Elantra (90k). After about an hour of highway driving (never before an hour, but sometimes not even after 2 hours) the car gets a serious shimmy like a wheel balance issue. The shimmy only occurs at highway speeds. The shimmy get slightly worse when I let off the accelerator and when I brake. The car also seems to lose some power when this shimmy starts, but that may just be the side effect of the shimmy. The real kicker is that when I pull off an exit and come to a stop (or get into stop and go traffic) and then return to highway speed the shimmy is gone.

I thought maybe a wheel bearing or a shifted belt, but I have ruled those out. Any suggestions?

Thanks

You might have something heating up from wear or from friction, such as a bearing or a rotor. When the shimmy starts, try touching carefully each wheel and see if one is hot. If so, have a shop check it out.

It’s also possible that a tire is heating up due to an internal defect. Again, touch the tires when thie symptoms happen and see if one is hot.

It might be easy to find the cause too by lightly running your hand over the treads of each tire. You might feel scalloping or other abnormal wear, and that can be a sign of what corner has the problem.

lastly, if none of these prove fruitful, there may be a worn suspension component. That’ll need to be checked.

This is not a tire issue. They would show up EVERY time you hit speed - not an hour or 2 later - and it would not disappear after you stop.

Look for a worn component, although I’m leaning towards a brake issue because of the loss of power.

Is the check engine light on? How old are the spark plugs & wires? Filters? (I will leave open the possibility that this is a poorly running engine).

Thanks for the replies. I’ll be sure to check the wheels for heating the next time it occurs.

I’ll check the rotors and brakes as well, I already checked the bearings so I don’t suspect they are an issue.

The check engine light is not on. Oil and air filters are clean.
Not sure on the spark plugs, would a misfiring spark plug only happen intermittently?

Ignition components are electrical. They can fail in all sorts of ways. One common way they show failure is when they get hot. They can also be more prone to show failure when the engine is put under load.

I’m just bringing it up because many people aren’t very good at figuring out what the actual source of a vibration/shimmy/whatever is. A rough running engine can feel like and be described as lots of different things. At 90K you’re either past due or about due to have the ignition components serviced anyway. So doing it is a good idea no matter what.

On the one hand, your “shimmy” description doesn’t really sound like a rough running car.

But one the other hand, the relation with time and having getting stuck in stop and go traffic clear it up for a while doesn’t sound like some kind of steering or suspension component.

To me it still sounds like something getting ho and then cooling downt. I’d not rule out an internal tire defect as a possibility.

Wish I could be there.

Cigroller,
An ignition problem should not be worse at idle than power in this case. OP said it got worse after backing off the pedal at highway speed. Time favors heat concepts. But where is the issue. A tire that goes funny when hot is a good possibility as the rubber softens with friction heat. But that is weird. Also once hot ignition issues should not be a stop and then drive fine issue as OP describes going to street traffic and back to the highway with no more issue.

euryale1, did I annoy you at some point in the past that now you’re tracking down my recent posts to tell me I’m wrong?

You know what? I often am wrong. In this case, I was just bringing up another possibility. And…when I was talking about ignition stuff I was answering the OPs question that appeared in a response.

If you like the tire thing that’s fine. Capriracer spends his entire life on tires - a total expert. You want to stay with tires, go to bat with him.

As I said in another post, if you have an alternative take just put it out there. I don’t need half-baked lectures from you, I assure you.

Ok, Sorry I dont spend each and every day here. Believe as you wish. Not my problem just pointing out that diagnostics sometimes gets stuck on our point of view.

My wag is a failing caliper. It works fine for so long then does not completely release when hot. A good brake diagnosis of inner and outer pads could be a good indicator.

Does the car pull a little to one side, then dodge the other way when you put on the brakes? I too think you have a brake caliper that’s sticking.