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hey guys, whenever my car sits for a couple hours and I start her up there is a very slight vibration from the engine for about 5 seconds. Its hardly noticeable, the rpms dont fluctuate, no SES light, after the 5 seconds the vibration goes away and it becomes a smooth idle. The car drives and feels great as far as acceleration and performance.
Could it be plugs? But then wouldnt the SES light be on?
 

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Unclear if this is a possible misfire/rough engine that does not trigger the CEL??

Suggest you check the first link below in my signature as it is likely you may have some leaking vacuum hoses or a bad DISA or DISA O-ring?
 

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but don't all misfires cause a CEL?
A lot of things can cause misfires, some don't trigger codes

Sent from my SPH-D700 using Bimmer App
 

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Not usually.
 

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When the engine is cold, the secondary air pump kicks in when you start it up, for a minute or two. It's possible that's causing the slight stumble you feel, as the engine management deals with the lean condition picked up by the oxygen sensors.
 

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Engine is in open loop, fixed fuel map, until O2 sensors warm up enough to toggle output Voltage beyond expected window. Engine is probably in open loop for the first 2-4 minutes depending on a number of conditions.
 

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My car has a very low frequency vibration as well at start up idle, though its not like a fast shaking but more like a suttle swaying. I've heard it mentioned in ohter threads before, and the proposed solution was new spark plugs. How many miles do you have on your current set of plugs? I plan on doing mine soon as I have heard they need to be changed every 50k.
 

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Mine doesn't do this. +1

Video or we can't help further.

I say 'we', I mean the people on here with uber bimmer knowledge :D
 

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I have slight vibrations at 2100, 1100, and some other random lower rpm. Hot or cold, doesn't matter.

No fault codes, check.
Compression tested, check.
Engine mounts, check.
Clutch, check.

Too many things are fine for me to bother looking further into it.
 

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Same problem here, 86K miles, just started this yesterday, car turns over, a few seconds later she'll start shaking, pretty rough, then the rest of the day no problems...In to see where this thread goes
 

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Same thing here; on a cold startup, it's as if there is very weak armed midget outside my car trying to test the jounce of my shocks for about a few seconds... Doesn't feel or sound like an engine stumble at all, it's literally as if someone is very mildly compressing & releasing my car's front suspension for a few cycles. My idle quality feels as if the engine is brand new on a cold start, just a bit higher in RPM for a minute, no sputtering or roughness like on my E36 M3.

I thought it was the mechanical cooling fan at first because it was toast; removed it & no effect besides 1 MPG higher on the OBC.

I'm guessing it's the harmonic balancer's viscous fluid being pooled on one side during a cold start. After a few seconds it spreads out evenly & does its job. Whether it's a sign that the balancer is worn out or wearing out in efficiency I do not know
 

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Same thing here; on a cold startup, it's as if there is very weak armed midget outside my car trying to test the jounce of my shocks for about a few seconds... Doesn't feel or sound like an engine stumble at all, it's literally as if someone is very mildly compressing & releasing my car's front suspension for a few cycles. My idle quality feels as if the engine is brand new on a cold start, just a bit higher in RPM for a minute, no sputtering or roughness like on my E36 M3.

I thought it was the mechanical cooling fan at first because it was toast; removed it & no effect besides 1 MPG higher on the OBC.

I'm guessing it's the harmonic balancer's viscous fluid being pooled on one side during a cold start. After a few seconds it spreads out evenly & does its job. Whether it's a sign that the balancer is worn out or wearing out in efficiency I do not know
The harmonic balancer has fluid inside?

or you talking about the fan clutch?
 

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My fan clutch is removed & yes it also has fluid inside. I know some harmonic balancers have a viscous fluid, Silicone based, inside for the dampening / energy conversion to heat. I would guess that most OE ones do due to their lower RPM benefits over a spring & elastomer based one (Google: Fluidamper vs ATI), but haven't actually looked into the oe one used in the E46.
 
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