N54 rough idle

John6857

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Aug 25, 2017
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2007 E90 335i 6MT
Hello all, i am stumped on what could be causing my rough idle. I have index 12's, ngk 95770(forgot what my shop gaped them to) carbon blast and new coils all withing 3 months. The only thing that hasn't been changed is my hpfp. I don't suspect it to be the hpfp since my rpms at idle aren't stumbling. Any input would be greatly appreciated.
Thanks!
 

Bmwfixerguy1

Lieutenant
Jun 5, 2017
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07 335i MT
Try bumping the idle a tad with mhd

Your precived idle can be different from another rough idle.. new motor mounts. Bump idle ect...

If it's an xi they idle a little rougher...
 

John6857

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Aug 25, 2017
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2007 E90 335i 6MT
Try bumping the idle a tad with mhd

Your precived idle can be different from another rough idle.. new motor mounts. Bump idle ect...

If it's an xi they idle a little rougher...
My car is rwd so that cant be it.My motor was replaced in august so i would assume if the mounts were shot the shop would have said something but i will look into the motor mounts.Could waste gate rattle attribute to a rough idle? my turbos are pretty shot.My idle is around 600-700,I have all the stuff to do mhd but i will raise the idle as a last resort.
 

dyezak

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May 4, 2017
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A video would help. What index are your injectors? How many miles on them? Does it idle differently when fully warmed up after driving than on a cold start?

Put a cup of water in your cup holder and video it at idle...it'll be a good visual of what's going on for those trying to help you.
 
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John6857

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Aug 25, 2017
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2007 E90 335i 6MT
A video would help. What index are your injectors? How many miles on them? Does it idle differently when fully warmed up after driving than on a cold start?

Put a cup of water in your cup holder and video it at idle...it'll be a good visual of what's going on for those trying to help you.
I will post up a video after work today. Index 12s and about 3k miles on them. I get weird "pops" on cold start. My idle is always rough, doesn't matter if its cold or warm. I will post up a vid of a semi warm start after work today and tomorrow morning a vid of a cold start.
 

dyezak

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May 4, 2017
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Thanks. We don't all have the same vocabulary for describing sounds, vibrations, feelings, etc. The video will help people cut through all that and hear for themselves what's going on. Not as good as being there in person, but certainly better than an eloquent poem lamenting the wonderful sounds of your N54 :)
 

08_335i

Sergeant
Nov 3, 2016
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2008 ST 335i
Video, log, etc. this is like saying help my car is wet and it was dry when I went to bed. Rain? Sprinklers? a*s hole with a bucket? who knows.
 

N54QC

Corporal
Aug 17, 2017
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07 E90 335i
Is your rpm's fluctuating at all? It could even be something like the DP's touching the subframe or engine and creating a vibration which makes it feel like it's idling rough.
 

John6857

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Aug 25, 2017
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2007 E90 335i 6MT
Is your rpm's fluctuating at all? It could even be something like the DP's touching the subframe or engine and creating a vibration which makes it feel like it's idling rough.
The rpms very rarely move at all. I will check the dP's
 

John6857

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Aug 25, 2017
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2007 E90 335i 6MT
This video is a start after a few hours of sitting
This video is after a drive home from work from idling

*Ignore the waste gate rattle*
 

dyezak

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May 4, 2017
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I'm not seeing a rough idle in those video's. I did hear a bit of a burble in the first one. You have new injectors plugs and coils. You can check the plugs just to be sure. Get the car up to temp. Park it then remove the plugs. If you have a black/wet plug it's just that injector. If all the plugs look good it might be your HPFP.
 

John6857

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Aug 25, 2017
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2007 E90 335i 6MT
I'm not seeing a rough idle in those video's. I did hear a bit of a burble in the first one. You have new injectors plugs and coils. You can check the plugs just to be sure. Get the car up to temp. Park it then remove the plugs. If you have a black/wet plug it's just that injector. If all the plugs look good it might be your HPFP.
I don't think the plugs are the problem but something is a little off so i will inspect them.
 

dyezak

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That test isn't to test the plugs. That test is to look at the plugs to see if the injectors are the problem.
 

John6857

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Aug 25, 2017
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2007 E90 335i 6MT
That test isn't to test the plugs. That test is to look at the plugs to see if the injectors are the problem.
Gotcha, i will check the plugs soon and update the thread soon.
Thanks!
 

doublespaces

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Oct 18, 2016
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So you've been having a rough idle for a few months? When exactly did you first notice this?