Rough idle at times.

bde · 08-30-2013, 01:07 PM

Hi there:

I have about 30k km on my 08 6MT M3 and I've been noticing some rpm variance at idle from maybe 550-525 (normal power setting). It will change pitch 3-4 times a minute for a couple of secs. Talked to the dealer and indy and they said the couldn't see anything wrong with the car.

Today after some spirited driving on power mode, I've noticed that once I stopped it was idling at 550 or so and than dropped to about 450 and you could feel the car shake a bit and have a feeling it was going to stall. It recovered to 550, did it one more time within 20secs or so but with less severe rpm drop.

I've tested the idle a few more times for about 2 mins. Slight 550-525 variance a couple of times but nothing else really.

This happens with engine fully warmed up at oil temp at about 100 (not when cold)

What gives? Is it an ICV issue perhaps? Is this normal?

Thanks!

radiantm3 · 08-30-2013, 01:30 PM

My car did that a lot before. Changed my spark plugs and it went away. Just one possible solution. Also maybe check for a dirty air filter?

bde · 08-30-2013, 02:53 PM

Thanks for the hints.

I'm changing all engine/cabin air filters 2nd week of september and hopefully this might take care of it. 30k km for a spark plug change- sounds early but I'll talk to my tech and see what he says.

GrussGott · 08-30-2013, 08:48 PM

Quote:

Originally Posted by bde

Thanks for the hints.

I'm changing all engine/cabin air filters 2nd week of september and hopefully this might take care of it. 30k km for a spark plug change- sounds early but I'll talk to my tech and see what he says.

Lots of other threads on this, but it could be hints of fuel filter, etc or, what I had, which is the beginning of the throttle actuator failing. Until it throws codes hard to know but like the other poster said there's some easy stuff you can do like plugs and/or fuel filter.

bde · 09-09-2013, 01:49 PM

Changed my oil and air filters today - not that.

Mechanic tested it and said one of the throttle actuators is going bad, but no CEL light yet...

Suggested to replace two of them since replacing one is iffy. Anyhow I decided to postpone it for a bit since it's $3,600CAD with tax and labour to replace a pair... Also I'm not really sure if it can be an ICV as well or instead of throttle actuator. Is it easy to determine if it's one and not the other when no CEL is triggered?

Does the max power output stay the same with these things going bad or is it still at 100%? Hard for me to tell.

Thanks!

08-30-2013, 01:07 PM	#1
bde Private First Class 48 Rep 194 Posts Drives: 2024 X3 M40i, AW Join Date: Oct 2009 Location: Toronto iTrader: (0) Garage List 2024 BMW X3 M40i [0.00]	Rough idle at times. Hi there: I have about 30k km on my 08 6MT M3 and I've been noticing some rpm variance at idle from maybe 550-525 (normal power setting). It will change pitch 3-4 times a minute for a couple of secs. Talked to the dealer and indy and they said the couldn't see anything wrong with the car. Today after some spirited driving on power mode, I've noticed that once I stopped it was idling at 550 or so and than dropped to about 450 and you could feel the car shake a bit and have a feeling it was going to stall. It recovered to 550, did it one more time within 20secs or so but with less severe rpm drop. I've tested the idle a few more times for about 2 mins. Slight 550-525 variance a couple of times but nothing else really. This happens with engine fully warmed up at oil temp at about 100 (not when cold) What gives? Is it an ICV issue perhaps? Is this normal? Thanks!
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08-30-2013, 01:30 PM	#2
radiantm3 Apex Everything! 976 Rep 4,378 Posts Drives: 2007 Honda S2000, 2017 GT350 Join Date: Sep 2008 Location: Cedar Park, TX iTrader: (6) Garage List 2011 E92 M3 [9.35] 2014 BMW i3 [10.00]	My car did that a lot before. Changed my spark plugs and it went away. Just one possible solution. Also maybe check for a dirty air filter? __________________ 2011 E92 M3(Sold). 2007 Honda S2000 (Track Car). 2016 Cayman GT4 (Sold). 2017 Shelby GT350 (AKA Crowd Killer). My pet project: https://stickershift.com
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08-30-2013, 02:53 PM	#3
bde Private First Class 48 Rep 194 Posts Drives: 2024 X3 M40i, AW Join Date: Oct 2009 Location: Toronto iTrader: (0) Garage List 2024 BMW X3 M40i [0.00]	Thanks for the hints. I'm changing all engine/cabin air filters 2nd week of september and hopefully this might take care of it. 30k km for a spark plug change- sounds early but I'll talk to my tech and see what he says.
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09-09-2013, 01:49 PM	#5
bde Private First Class 48 Rep 194 Posts Drives: 2024 X3 M40i, AW Join Date: Oct 2009 Location: Toronto iTrader: (0) Garage List 2024 BMW X3 M40i [0.00]	Changed my oil and air filters today - not that. Mechanic tested it and said one of the throttle actuators is going bad, but no CEL light yet... Suggested to replace two of them since replacing one is iffy. Anyhow I decided to postpone it for a bit since it's $3,600CAD with tax and labour to replace a pair... Also I'm not really sure if it can be an ICV as well or instead of throttle actuator. Is it easy to determine if it's one and not the other when no CEL is triggered? Does the max power output stay the same with these things going bad or is it still at 100%? Hard for me to tell. Thanks!
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