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Thread: Slight rumble?

  1. #11
    Join Date
    Jan 1970
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    Branford, CT
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    15,671
    Quote Originally Posted by Fried_Chicken View Post
    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).
    Quote Originally Posted by Yankeefan View Post
    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.

    Sent from my Pixel 3 using Tapatalk
    BP
    2005 330i ZHP / 6MT
    Imolarot / Naturbraun



    It's not the car you drive, it's how you drive it.

  2. #12
    Join Date
    Oct 2016
    Location
    Vermont
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    509
    If it's actually a sort of "burbling", I wonder if it could be related to a minor manifold/exhaust leak?
    2004 BMW 330i ZHP (50k miles), Jet Black with black leather, MFactory LSD (3.38) with Z4 cover, 18"x8.5" ET38 APEX Arc-8's (Anthracite) with 245/40 Michelin PSS', Koni Sports with factory springs and front and rear reinforcement plates, Shark Injector, Corsa TSE3 cat-back exhaust, TMS under-driven pulleys (water & steering), CDV delete, TMS CF strut brace, K&W CAI, GAS DISA rebuild, TMS pedals, Wheelskins steering wheel cover, roller tray center console, and WeatherTech floor and cargo mats

  3. #13
    Quote Originally Posted by az3579 View Post
    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.

    Sent from my Pixel 3 using Tapatalk
    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.

  4. #14
    Quote Originally Posted by az3579 View Post

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

    Sent from my Pixel 3 using Tapatalk
    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.
    1991 E30 Alpinweiß 325iX [SOLD]
    2005 E46 Sparkling Graphite Metallic 330Ci ZHP 6spd

  5. #15
    Quote Originally Posted by Reasoned1 View Post
    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.
    1991 E30 Alpinweiß 325iX [SOLD]
    2005 E46 Sparkling Graphite Metallic 330Ci ZHP 6spd

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