Lumpy Vibration at Idle

[ChrisV990]

Okay so clearly something strange is going on with my car. I am pretty sure this has been going on ever since I bought it a few months ago but it's hard to say for sure since it's only noticeable if you're really paying attention (and also really anal like myself).

When you are sitting in the car at idle you can feel a lumpy vibration. It isn't the idle itself, it feels like a lopsided circle is spinning because the car moves back and forth really inconspicuously at idle. The ONLY time this happens is at idle, never any other time. No one else notices it but me, not even my wife who is always in the car with me.

The only things I can even begin to think of off the top of my head would be bad engine mounts or maybe a flywheel / clutch setup that wasn't properly balanced. The car has the stock clutch and flywheel though the previous owner did mention that it had been replaced with a new stock clutch and flywheel at some point.

Any ideas what this might be? Like I said, you really have to be paying attention to notice it but it's enough to bother me. I'm going to replace the engine mounts for the hell of it since they look like they could use replacing. As for the clutch / flywheel, that's on my to-do list.

[Intestines]

Could be the dual mass flywheel or a bad driveshaft. I have the same vibration but I know it's the driveshaft. Just can't afford a replacement at the time. I'm in a 95 m3 FYI.

[DrewMontE36]

pre detonation?

[ChrisV990]

Could be the dual mass flywheel or a bad driveshaft. I have the same vibration but I know it's the driveshaft. Just can't afford a replacement at the time. I'm in a 95 m3 FYI.

I don't think it would be the driveshaft because the only time it ever happens is when I am sitting at idle not in gear. The driveshaft isn't spinning unless the gear is engaged so I think that rules it out, no?


pre detonation?

Not sure I follow... It's just happening at idle while in neutral. Once you put it in gear and go it can't be felt anymore (but for all I know it's still happening).

[aeronaut]

So even 100rpm above idle, the lumpiness goes away?
Could certainly be engine mounts to me.

[rajicase]

pre detonation?

Give this some thought actually. Its more likely than you think to be a misfire/pre detonation/fuel injector issue than you think.

These can cause your car to 'rock' back and forth a little as its struggling to run. I would try and pull codes if I were you.

When I had my fuel injector issue, at idle the car would sound lumpy and run poorly, and it would rock the entire car back and forth.

[berny2435]

The pre-detonation or bad injector could cause a lumpy idle. you might notice some other performance issues as well but idle is a different animal than full, light or on off throttle though. Bad fuel pressure could even cause it.

Is it constant? or just everyonce in a while?
Does it happen at idle, without the clutch engaged?

Possibly the flywheel is not moving freely as they are a mechanical part. My limited understanding of a Dual mass Flywheel is that they absorb vibration (mainly with springs) by allowing an offset of rotation b/t the motor and the clutch. I wouldn't say it's out of ballance but more likely it has worn parts (springs) or the harmonic vibrations of the car have changed in which the DMF is not longer able to tune out the vibrations as well. I may have felt this sensation before but I have BMW group N motor mounts and it's definitely not constant. I looked back through my cars documentation the other day and I couldn't find anything clutch or flywheel related but the guibo has been replaced and there's no paperwork of that. I'm hoping that the clutch was done at min. It feels strong and grips well at 110K.

http://www.youtube.com/watch?v=MfNjARZc5Wo


http://forums.bimmerforums.com/forum/showthread.php?1122162-Anyone-ever-break-a-dualmass-flywheel
486814

not E36 but a DMF designed to fit SMG system in M5 or M6 only S85 V10
Dates: May 2003 to Feb 2009
486813
http://www.motor-haus.co.uk/images/source/llluk5.jpg

[ChrisV990]

Here's the thing though guys, the lumpy vibration has nothing to do with the idle. The car actually idles just fine.

The vibration feels like it's coming from the motor or drive train instead. It only happens (or at least you can only feel it) when the car is in neutral sitting at idle. Once you get going it goes away (or at least can't be felt).

I probably ought to check the fuel and spark just to make sure but basically the best way I can describe it is that it seems like I can feel the motor or the flywheel spinning around in the car and somehow it's not balanced because it has a lumpy vibration to what should be a smooth movement. Ugh, it's hard to explain in words, haha.

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Is it constant? or just everyonce in a while?
Does it happen at idle, without the clutch engaged?


It is constant as long as you're at idle in neutral.

It happens at idle only without the clutch engaged. Once you engage the clutch and go you can no longer feel or (or you're just getting up to speed so that's drowning out the vibration with other road vibrations).

[Stephen Max]

It is constant as long as you're at idle in neutral.

It happens at idle only without the clutch engaged. Once you engage the clutch and go you can no longer feel or (or you're just getting up to speed so that's drowning out the vibration with other road vibrations).

A worn out dual mass flywheel will manifest itself mainly at idle and in neutral, with the clutch pedal not depressed. Once you depress the clutch pedal, you axially load the flywheel through the throwout bearing, which suppresses any looseness in the flywheel. Does that match your experience?

[berny2435]

Here's the thing though guys, the lumpy vibration has nothing to do with the idle. The car actually idles just fine.

The vibration feels like it's coming from the motor or drive train instead. It only happens (or at least you can only feel it) when the car is in neutral sitting at idle. Once you get going it goes away (or at least can't be felt).

I probably ought to check the fuel and spark just to make sure but basically the best way I can describe it is that it seems like I can feel the motor or the flywheel spinning around in the car and somehow it's not balanced because it has a lumpy vibration to what should be a smooth movement. Ugh, it's hard to explain in words, haha.

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It is constant as long as you're at idle in neutral.

It happens at idle only without the clutch engaged. Once you engage the clutch and go you can no longer feel or (or you're just getting up to speed so that's drowning out the vibration with other road vibrations).

I might be stating the obivous here, but there is a difference b/t 1.) idle with clutch attached/peddle not depressed, and 2.) clutch depressed (nothing touching flywheel). Even at idle, the clutch is on the flywheel, idler gears are spining in the transmission.

Having the weight of the clutch against the flywheel gives it some resistance and even more momentum. if the momentum is interupted by another pulse from a bad tune or faulty fuel delivery, that momentum is lost and has to be gained again and will cause the DMF to move around. This could give a judder.

Without the clutch engaged at idle, I'd think that the weight of the dual mass flywheel by itself wouldn't have an juddering effect on the car b/c it's very little weight, but if it is, this obviously points towards the flywheel having some issues.

You are on the other thread about changing out the clutch and flywheel so maybe this will take care of it. I'd check the easy stuff first before doing the flywheel and clutch though.

[ChrisV990]

A worn out dual mass flywheel will manifest itself mainly at idle and in neutral, with the clutch pedal not depressed. Once you depress the clutch pedal, you axially load the flywheel through the throwout bearing, which suppresses any looseness in the flywheel. Does that match your experience?

I would say that matches my experience pretty perfect. Sounds like it very well may be the flywheel. Looking at the maintenance history from the previous owner he said the clutch was changed but he makes no mention at all of the flywheel every being changed or resurfaced so my guess is I've got a stock flywheel in there with 200k miles on it.

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You are on the other thread about changing out the clutch and flywheel so maybe this will take care of it. I'd check the easy stuff first before doing the flywheel and clutch though.


Yep, you're right. The bottom line is this car has 200k miles on it though so a host of things need to be fixed. I'm going through replacing every single bushing on the car. The oil pan gasket needs to be done so at the same time I ought to do the motor mounts. The rear main appears to be leaking (not 100% sure yet) so if that's going to be changed then there's no point in not doing the clutch / flywheel at the same time, especially since it's all mystery miles since it's a pretty new car to me.