Diagnose a car wobble

Factual Questions
1

My 2012 VW Jetta TDI manual has developed a strange intermittent wobble.

I have a 50 mile commute each way. In the beginning (last December), the car would be quite smooth only to start to wobble a bit after a good 20 miles. That wobble would increase and usually not go away for the remainder of the commute.

The wobble was less severe on really cold days.

The wobble can be felt in the floor by my feet/pedals and in the seat, but never in the steering wheel.

I’ve tried putting the car into neutral and no change happens.

It seems to smooth when I speed up and worsen when I let off the throttle and coast.

It happens the same at any RPMs.

I can swear a few times I have felt the engine stumble and surge when it happens.

The wobble itself feels like a tire is out of balance. It will also feel like the tires “hop”. I have had the tires balanced 3 times at two different dealers, one of which used a Road Force Balancer. No change was noticed.

The car has also had a full alignment and two tires replaced (they had a little feathering). That made it feel smoother in general, but that underlying intermittent wobble is still there.

As for the intermittent part: I drove the car a lot on Saturday. I think I probably did 175 miles of mixed driving. The weather was warm and nice. Throughout, the car was smooth as glass.

But then last night, on my commute home, the car was quite rough, again feeling like I had a square tire on it.

Since it is intermittent, I have had a very difficult time reproducing it to a degree that the Dealer can diagnose it (they will feel only a slight wobble and say it is normal/road interference).

As can be guessed, I am extremely frustrated with this car!

Assuming the tires and wheels are fine (which repeat balancing suggests), what else can it be? How can it be so smooth sometimes, only to be so rough at others?

2

Well it certainly isn’t the spark plugs!

I’d look for a broken engine or transmission mount.

3

Intermittent. The one word that keep mechanics and IT people up at night.

4

Agreed. Very frustrating on my end to be driving it and want to drive it into a bridge abutment when it gets bad. Then I bring it to the dealer and the wobble isn’t bad :smack:

5

Does it ever wobble with the clutch disengaged?

6

Really sounds like a broken engine or tranny mount, on an eleven year old car this would be reasonable.

IOW JerrySTL probably is right

Capt

7

Sorry, got distracted. I had a mystery wobble once that turned out to be the clutch actuator fork being a little off and misaligning the plates just a tiny bit. Even in neutral the clutch is engaged and I suppose the wobble could occur, although I don’t recall it ever wobbling in neutral when I had that problem.

8

Longshot (but the other logical ideas surrounding tires seem to be eliminated): I’m assuming you’ve got yourself a 4-cylinder motor. If one cylinder isn’t firing, you’ll definitely feel it as an interruption in what is expected to be a steady stream of power pulses.

Worse, if it IS a misfire, it might only do it when you’re pressing the accelerator or subjecting the car to some condition that is irritating one or more of the 600 electrical components that all talk to each other and decide how much gas to put into a cylinder and when/whether to fire it. So, it might like running under some conditions and not others. Of course, I would expect a misfire to trip your check-engine light.

  • whisper whisper whisper 1 year old whisper whisper *
9

If the wobble is less on real cold days it is possible you are getting a misfire or arcing in your wires. Cold days are drier and less prone to carrying leaking current.

10

if it feels like an out of balance tire, but it isn’t, and you don’t feel the vibration through the steering wheel (like you would if it was an out of balance tire or stuck caliper) and it’s intermittent, it’s probably power train related. and since it’s a VW, I wish you the best of luck.

11

Rather negated by this from the OP: “It seems to smooth when I speed up and worsen when I let off the throttle and coast.” That’s not a misfire.

12

Bearings.

13

That’s my fear. Though there’s still 9000 on the warrantee.

14

Good point, that actually sounds more like tires, in recent years tires have changed where they tend to vibrate more at lower speeds instead of highway speeds. I have noticed this on heavy duty trucks as well as automotive tires. Very slight wear on steering componets can exagerate the problem.

15

The tires were balanced 3 times and the worse two were replaced. All of that did nothing to the wobble.

It feels like a tire, but I really don’t see how it can be.

16

Been there done that (and fixed the car too)
You have a bad axle/CV joint. Yes they can be intermittent.
Had a lady with a brand new XC90 that had a mysterious wobble/ vibration that we could never duplicate.
One day I had a retired technical specialist in my office when she called to rip my head off.
After the call was over he told me he had encountered this issue and it was axles.
So i put a couple of axles in the car and the lady thinks I am a genius.
I had 2 or 3 others with the same nebulous wobble complaint that I fixed with new axles.
So you might want to chat with the service manager and tell him what this service manager found.
Good luck.

17

Only if you assume the ECU has cut fuel to the injectors during the deceleration, and so there’s no compression mismatch–and that whole ECU/injectors thing is debatable. :smiley: * cowers in the corner *

Rick: had no idea axles could be intermittent. But on a modern VW wouldn’t there only be axles on the front? And if those were bad, wouldn’t that transfer into the steering wheel? If it’s a rear problem–bearings, like Buster ChiChi suggests? On a 1 year old car?

18

Oops I cannot read, sorry. I have to doubt my previous diagnosis because unless you are doing something crazy with the car they should no be broken. Good luck

Capt

19

There is no doubt that the injectors are shutting off on deceleration. If they weren’t there would be other issues with the car. As a wise training instructor once said if there is no fire there can be no misfire. And since there is no fuel there is no fire. If there was such a compression issue that you could feel it on decel you would for sure feel it on accel and you would have misfire codes. I would just about bet my paycheck it isn’t a misfire unless there are symptoms I am unaware of.

Yes it would be the front axles with CV joints. The issue is with a wobble in the joint. And yes they can be intermittent.

20

I was going to say your hub bearings are going but i defer to Rick in most diagnoses. Distant possibilty is failed muffler bushing that lets something rub when power lets off.