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Persistent rough running, vibration


Mowgli1647545497

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Hi all,

 

Abit back I posted about a growing vibration issue I've been having in my 04 V.

 

As a recap: the engine is running rougher or imparts more vibration to to cockpit. Its growing in intensity over time.

 

It vibrates most as certain RPMs and at others its more quiet. Its a function of engine RPM and not road speed or gear engagement (although having the gears engaged seems to impart more vibration to the body/chassis).

 

Since I originally wrote I've done the following:

- inspected the motor and tranny mounts (all are fine, solid and tight with not looseness and all in spec.

- changed the plugs and a couple of the plug wires

- run a few tanks with injector cleaner

- new filters

- had the codes checked by a tech (no thrown codes or anything like that)

 

This has slightly helped the vibration but not removed it.

 

The car is at 84,000 and has had regular servicing. MPG has not dropped off.

 

I'm at a loss. If this were an old car I'd say a carb-cleaning/timing etc. But I just don't know. When the mounts checked out it really took away the one thing I thought Iit could be.

 

I'm wondering - could injectors be the culprit?

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Good idea, not dumb, Nate. Thx I'll look into that. Seems a slim possibility, given the force with which it can vibrate the whole car, but worth a look.

 

Jason, its not just at idle but really any multiple of 1500rpm. Its worst at 1500rpm but it has some harmonic vibration on rpm multiples above that.

 

Reason I don't think its the tranny is it does it even when not in gear, but just sitting in neutral too.

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tl;dr Cars' are kinda smart these days, shoulda got a SES light

 

The EPA mandates misfire detection to the Nth degree, and the error for crank speed acceleration per cycle at a given RPM is not very much. Not to say it wouldn't be something combustion driven, but I would think you would get strange variations in the cycle data or at minimum the pre-cat primary O2 sensor(s) stream.

 

Maybe something rotational in the drivetrain, FW or PP?

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Good idea, not dumb, Nate. Thx I'll look into that. Seems a slim possibility, given the force with which it can vibrate the whole car, but worth a look.

 

Jason, its not just at idle but really any multiple of 1500rpm. Its worst at 1500rpm but it has some harmonic vibration on rpm multiples above that.

 

Reason I don't think its the tranny is it does it even when not in gear, but just sitting in neutral too.

 

Every 1500 make me think its a balancer issue.. good time to upgrade

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