Slightly rough idle

kaktustsar · 09-10-2023, 03:05 AM

My e90 is experiencing a small fluctuation in RPM while idling (both in D and N), I would say around 50, but I cannot hear the difference in engine sound. Otherwise car behaves normally (at least to my knowledge).

It is same in cold start and when it is warmed up.

I would also underline that this happens sometimes.

Error codes reading shows 4166, 4CF3, 49F2 (car electric said there are sporadic and he turned it off - not showing again, related to the DPF. And also 4222 - second glow plug, but only degradation, not complete failure as I was explained)

Should I be worried and get it checked, or this is normal behavior? Also while at the topic, what kind of RPM fluctuation is a reason to start worrying?

Since gif is not working:
https://im.ezgif.com/tmp/ezgif-1-f4652ec461.gif

crashoverride · 09-11-2023, 12:12 PM

Does the idle smooth out when AC is turned off..???

kaktustsar · 09-11-2023, 12:30 PM

Thanks for reply.
All is with AC off. Although today it didn't happen at all.

Also I did a little "inspection" under the hood this morning and found out the intake hose is bad. Could it be the culprit?

crashoverride · 09-13-2023, 04:27 PM

The e90 is very picky about air leaks in the engine. The MAF sensor is located before that hole in your picture. So the engine is expecting X amount of air but that hole can change up or down how much and possibly be the culprit. This is one of the few times that using duct tape can determine if that is leading to the problems you are having. Seal that spot up with duct tape (tie a rag shirt etc) if it fixes get it repaired.

Keep the future readers updated when you come across a fix please.

kaktustsar · 09-14-2023, 12:14 PM

Thanks for the advice and reply

Update on the situation. I've got the intake hose replaced. It is better now but I still saw the the same behavior.
What I (maybe) failed to realize before is that steering wheel was reeled (if this is the right word) into one side. After putting it up straight the RPM stabilized!
So, to make things clear, I am where while reeling the wheel, because of the servo pump, it will cause instability in the RPM, but in this case it was steady and reeled up at some degree either to left or right.

Never with wheels straight up I observed RPM instability.
Additional question here could be if this is a problem of its own, that in some position of the steering wheel, servo pump goes on/off constantly or is working when it shouldn't be?

I cannot guarantee this was the problem, nor it is solved. Just sharing my experience, and if somebody can confirm it makes sense, would love to hear it this can be the root cause

09-10-2023, 03:05 AM	#1
kaktustsar New Member 0 Rep 7 Posts Drives: E90 320d Join Date: Sep 2023 Location: Serbia iTrader: (0)	Slightly rough idle - automatic transmission My e90 is experiencing a small fluctuation in RPM while idling (both in D and N), I would say around 50, but I cannot hear the difference in engine sound. Otherwise car behaves normally (at least to my knowledge). It is same in cold start and when it is warmed up. I would also underline that this happens sometimes. Error codes reading shows 4166, 4CF3, 49F2 (car electric said there are sporadic and he turned it off - not showing again, related to the DPF. And also 4222 - second glow plug, but only degradation, not complete failure as I was explained) Should I be worried and get it checked, or this is normal behavior? Also while at the topic, what kind of RPM fluctuation is a reason to start worrying? Since gif is not working: https://im.ezgif.com/tmp/ezgif-1-f4652ec461.gif Attached Images Last edited by kaktustsar; 09-10-2023 at 03:07 AM.. Reason: link added for gif
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09-11-2023, 12:12 PM	#2
crashoverride Lieutenant 178 Rep 582 Posts Drives: na Join Date: Jul 2006 Location: na iTrader: (0)	Does the idle smooth out when AC is turned off..???
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09-11-2023, 12:30 PM	#3
kaktustsar New Member 0 Rep 7 Posts Drives: E90 320d Join Date: Sep 2023 Location: Serbia iTrader: (0)	Thanks for reply. All is with AC off. Although today it didn't happen at all. Also I did a little "inspection" under the hood this morning and found out the intake hose is bad. Could it be the culprit? Attached Images
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09-13-2023, 04:27 PM	#4
crashoverride Lieutenant 178 Rep 582 Posts Drives: na Join Date: Jul 2006 Location: na iTrader: (0)	The e90 is very picky about air leaks in the engine. The MAF sensor is located before that hole in your picture. So the engine is expecting X amount of air but that hole can change up or down how much and possibly be the culprit. This is one of the few times that using duct tape can determine if that is leading to the problems you are having. Seal that spot up with duct tape (tie a rag shirt etc) if it fixes get it repaired. Keep the future readers updated when you come across a fix please.
	Appreciate 0 Quote

09-14-2023, 12:14 PM	#5
kaktustsar New Member 0 Rep 7 Posts Drives: E90 320d Join Date: Sep 2023 Location: Serbia iTrader: (0)	Thanks for the advice and reply Update on the situation. I've got the intake hose replaced. It is better now but I still saw the the same behavior. What I (maybe) failed to realize before is that steering wheel was reeled (if this is the right word) into one side. After putting it up straight the RPM stabilized! So, to make things clear, I am where while reeling the wheel, because of the servo pump, it will cause instability in the RPM, but in this case it was steady and reeled up at some degree either to left or right. Never with wheels straight up I observed RPM instability. Additional question here could be if this is a problem of its own, that in some position of the steering wheel, servo pump goes on/off constantly or is working when it shouldn't be? I cannot guarantee this was the problem, nor it is solved. Just sharing my experience, and if somebody can confirm it makes sense, would love to hear it this can be the root cause
	Appreciate 0 Quote