Slight rumble?

[Dano516]

Hi all,

Can’t find any other explanations on the internet, and I guess since I’m not the best versed at anything specific, I’d ask here.

Whenever I’m coming to a stop, eventually going from 1st to neutral, I feel a slight rumble in the car just about a second while coming to a stop.

The clutch has never been done, as my seller beforehand saw no previous need to.

Anything would be appreciated!

[Fried_Chicken]

injectors reactivating

[az3579]

injectors reactivating?
We don't have cylinder deactivation as a feature...

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[Fried_Chicken]

?
We don't have cylinder deactivation as a feature...

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Yes we do

[Oli77]

Wait are you downshifting in first gear?

A rumble on starting in first makes more sense.

[az3579]

Yes we doNo... We don't. Lol

Cylinder deactivation insuinuates the ability to drive with a certain number of cylinders not active. Our M54 engines do not have this feature. It's either all injectors firing (in their respective orders) or none at all (off throttle deceleration). Their transition from off to on is seamless, unlike some cars with actual cylinder deactivation, which you can sometimes feel depending on load or engine.



Wait are you downshifting in first gear?

A rumble on starting in first makes more sense.

A rumble when first starting off could be a bad guibo or maybe diff bushings. Usually driveline related in this case, some sort of rubber failing.

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[Fried_Chicken]

No... We don't. Lol

Cylinder deactivation insuinuates the ability to drive with a certain number of cylinders not active. Our M54 engines do not have this feature. It's either all injectors firing (in their respective orders) or none at all (off throttle deceleration). Their transition from off to on is seamless, unlike some cars with actual cylinder deactivation, which you can sometimes feel depending on load or engine.




A rumble when first starting off could be a bad guibo or maybe diff bushings. Usually driveline related in this case, some sort of rubber failing.

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We have “off throttle decelration”. Where all the ciylinders get deactivated. Cylinder. Deactivation. Only while in gear.
Right before coming to a stop, the injectors will start up again, and this can be felt as a *very* slight rumble.

[Dano516]

Wait are you downshifting in first gear?

A rumble on starting in first makes more sense.

Well I’m coming to a stop, from first to neutral. Only after I come to a full stop, I feel the slight rumble for about one second. Also, at times, it seems as if I can’t shift into first, as the shifter stops in between neutral at first. A few friends recommended I do a transmission fluid change first to see if that fixed anything. The clutch has never been done and I’m at about 96k miles so I guess I’ve answered my own question hahah.

[Oli77]

So the rumble has nothing to do with the clutch if you feel it only when at a full stop.

I would look at the idle control valve (ICV) maybe, could be sticking?

I always downshift to second if I am coming to a complete stop and then go into neutral. I never downshift into first, or very rarely, if I need to get going right soon.

[Yankeefan]

We have “off throttle decelration”. Where all the ciylinders get deactivated. Cylinder. Deactivation. Only while in gear.
Right before coming to a stop, the injectors will start up again, and this can be felt as a *very* slight rumble.

Is this why the transition from very slight throttle to zero throttle (and sometimes vice versa) can feel like stuttering/shaking?

[az3579]

We have “off throttle decelration”. Where all the ciylinders get deactivated. Cylinder. Deactivation. Only while in gear.
Right before coming to a stop, the injectors will start up again, and this can be felt as a *very* slight rumble.

That isn't 'cylinder deactivation', that's just how fuel injected vehicles are designed. 'Cylinder deactivation' is an actual gas saving feature of some V6 and V8 cars where it disables a certain number of cylinders (not all) while at steady state cruising, hence why I'm making it such a point to be careful with using that terminology as it can confuse people.

And no, there is no rumble when they reactivate on our M54's, not on a properly running car at least. The OP said this is happening when coming to a stop going from 1st to neutral. By then the injectors have long reactivated (they kick in once the revs hit 1200RPM or below).
Is this why the transition from very slight throttle to zero throttle (and sometimes vice versa) can feel like stuttering/shaking?I think you're feeling something else, not the injectors kicking in/shutting off. Are your engine, tranny, and diff mounts good condition? Guibo?

In a normally operating engine, you'll never feel your injectors activating/deactivating.



OP, you really should take a video of this happening so we can see what is going on when you say it vibrates.

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[Reasoned1]

If it's actually a sort of "burbling", I wonder if it could be related to a minor manifold/exhaust leak?

[Fried_Chicken]

That isn't 'cylinder deactivation', that's just how fuel injected vehicles are designed. 'Cylinder deactivation' is an actual gas saving feature of some V6 and V8 cars where it disables a certain number of cylinders (not all) while at steady state cruising, hence why I'm making it such a point to be careful with using that terminology as it can confuse people.

And no, there is no rumble when they reactivate on our M54's, not on a properly running car at least. The OP said this is happening when coming to a stop going from 1st to neutral. By then the injectors have long reactivated (they kick in once the revs hit 1200RPM or below). I think you're feeling something else, not the injectors kicking in/shutting off. Are your engine, tranny, and diff mounts good condition? Guibo?

In a normally operating engine, you'll never feel your injectors activating/deactivating.



OP, you really should take a video of this happening so we can see what is going on when you say it vibrates.

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I was teasing you on cylinder deactivation, I know what it is :P

But I do feel it; if I'm in gear decelerating, I ever so slightly nudge the gas pedal, i'll feel the engine do its thing. Same when coming to a complete stop in gear, at some low RPM the cylinders kick in again.

It did it before and after I replaced my injectors with cleaned injectors.

[Dano516]

OP, you really should take a video of this happening so we can see what is going on when you say it vibrates.

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Welp I don’t think I notice it happening enough, also, it wouldn’t be shown on video. However, the explanation with the injectors seems fairly applicable. The car altogether still runs like a dream so it doesn’t hold for crazy concern.

Thank you all for your help though.

[Dano516]

If it's actually a sort of "burbling", I wonder if it could be related to a minor manifold/exhaust leak?

I doubt it, the rumbling is only through feel and it lasts half a second at most.