N52 random rpm surge at idle.

Serf27 · 10-10-2019, 03:08 AM

Hi all, I've got an issue than I've been putting up with but am now ready to fix it as I'm taking the car on a long 8hr trip this Friday!

When stopped, the rpm will drop about 150-200 rpm then spike back up, this causes something to rattle. Not sure if the rattle is related to the rpm or if its something loose and just rattling when the rpm drops.
The rpm drop is very annoying.
the rpm jump is not huge. with idle at about 700, it'll drop 200 then go right back up to 700
No issues while driving and no SES light.

I'm going to change the plugs tomorrow and clean the vanos solenoid.

Anything else I should look at?
I haven't found a thread describing my exact issue.

Thanks.

Meeni · 10-10-2019, 09:34 AM

Is it the AC turning on maybe? Some level of drop is normal when that happens. However that seems like too much. I would indeed start by looking at the VANOS. Also check the oil filter cap for missing parts (causing low oil pressure, there are multiple threads explaining this issue).

Serf27 · 10-10-2019, 12:04 PM

I’ll look into the oil cap. I had never heard of this! Thank you.

I know the ac drop you’re referring too and this isn’t the case.

The rpm drop will happen the whole time I’m at idle waiting, not just once.

It will go down-up-down-up maybe stay still for a second then back down and up.

Denny347 · 10-10-2019, 08:32 PM

PCV going bad perhaps

Serf27 · 10-11-2019, 03:16 AM

Thanks for that.
However I don’t have time to do the PCV right now before the trip.

Today it hardly did the surging, it was colder though than the last few days.

I saw another thread that describes similar issues that lead to a coil being just bad enough to lightly stumble but not throw a code.

I will embark on my trip with a few spare coils and hope for the best!

Meeni · 10-11-2019, 07:29 AM

Did you look at the codes ? I would start by plugging in INPA or ISTA to get some readings from the shadow errors and looks at the 'smoothness' test before throwing parts at the problem randomly.

Serf27 · 10-11-2019, 09:08 AM

I hooked up bimmer geeks ProTool which is near the same as inpa for reading shadow codes isn’t it?

No codes popped up at all. Besides transmission fluid quality.

porsche959 · 10-11-2019, 09:30 AM

Spray some carb cleaner around the engine. If it revs up, you have a vacuum leak.

NOKO · 10-11-2019, 11:54 AM

I had this same issue and solved it by removing and cleaning the vanos solenoids. It's a really common problem since oil builds up in and around the solenoids. They are very easy to remove and clean and shouldn't take longer than 30min

Fritzer · 10-11-2019, 11:55 AM

Is your issue similar to this?

https://www.e90post.com/forums/showthread.php?t=1601784

HUMBLEN52 · 04-02-2024, 10:59 PM

Hey any luck with a fix for this issue? My 2010 528i xdrive E60 model is doing the same thing I can’t figure out what it could be, any help is appreciated

wrevilo · 04-03-2024, 09:23 AM

Quote:

Originally Posted by NOKO

I had this same issue and solved it by removing and cleaning the vanos solenoids. It's a really common problem since oil builds up in and around the solenoids. They are very easy to remove and clean and shouldn't take longer than 30min

Doing this on my N52 130i resolved my hot idle issues.

Serf27 · 04-05-2024, 12:03 AM

I never figured it out.
I cleaned the vanos solenoids once and the issue continued.

10-10-2019, 03:08 AM	#1
Serf27 Brigadier General 2851 Rep 4,322 Posts Drives: 335i Join Date: Apr 2018 Location: Sitting in a BMW. iTrader: (-1)	N52 random rpm surge at idle. Hi all, I've got an issue than I've been putting up with but am now ready to fix it as I'm taking the car on a long 8hr trip this Friday! When stopped, the rpm will drop about 150-200 rpm then spike back up, this causes something to rattle. Not sure if the rattle is related to the rpm or if its something loose and just rattling when the rpm drops. The rpm drop is very annoying. the rpm jump is not huge. with idle at about 700, it'll drop 200 then go right back up to 700 No issues while driving and no SES light. I'm going to change the plugs tomorrow and clean the vanos solenoid. Anything else I should look at? I haven't found a thread describing my exact issue. Thanks. __________________ E90 335i-408WHP. Alpine over Terra brown E70 X5 35i M Sport-Stage1 Tune. Alpine over Black E91 328 M Sport-Alpine over Black-Alpine over Saddle brown. E93 335i-DINAN tuned. Alpine over Saddle brown Last edited by Serf27; 10-10-2019 at 03:15 AM..
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10-10-2019, 09:34 AM	#2
Meeni Gateropode 329 Rep 2,848 Posts Drives: BMW 330i 06 Join Date: Apr 2012 Location: TN iTrader: (0)	Is it the AC turning on maybe? Some level of drop is normal when that happens. However that seems like too much. I would indeed start by looking at the VANOS. Also check the oil filter cap for missing parts (causing low oil pressure, there are multiple threads explaining this issue).
	Appreciate 0 Quote

10-10-2019, 12:04 PM	#3
Serf27 Brigadier General 2851 Rep 4,322 Posts Drives: 335i Join Date: Apr 2018 Location: Sitting in a BMW. iTrader: (-1)	I’ll look into the oil cap. I had never heard of this! Thank you. I know the ac drop you’re referring too and this isn’t the case. The rpm drop will happen the whole time I’m at idle waiting, not just once. It will go down-up-down-up maybe stay still for a second then back down and up.
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10-10-2019, 08:32 PM	#4
Denny347 Major 347 Rep 1,076 Posts Drives: 2008 M3 E90 Join Date: Aug 2010 Location: Indianapolis, IN iTrader: (0)	PCV going bad perhaps
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10-11-2019, 03:16 AM	#5
Serf27 Brigadier General 2851 Rep 4,322 Posts Drives: 335i Join Date: Apr 2018 Location: Sitting in a BMW. iTrader: (-1)	Thanks for that. However I don’t have time to do the PCV right now before the trip. Today it hardly did the surging, it was colder though than the last few days. I saw another thread that describes similar issues that lead to a coil being just bad enough to lightly stumble but not throw a code. I will embark on my trip with a few spare coils and hope for the best! __________________ E90 335i-408WHP. Alpine over Terra brown E70 X5 35i M Sport-Stage1 Tune. Alpine over Black E91 328 M Sport-Alpine over Black-Alpine over Saddle brown. E93 335i-DINAN tuned. Alpine over Saddle brown
	Appreciate 0 Quote

10-11-2019, 07:29 AM	#6
Meeni Gateropode 329 Rep 2,848 Posts Drives: BMW 330i 06 Join Date: Apr 2012 Location: TN iTrader: (0)	Did you look at the codes ? I would start by plugging in INPA or ISTA to get some readings from the shadow errors and looks at the 'smoothness' test before throwing parts at the problem randomly.
	Appreciate 0 Quote

10-11-2019, 09:08 AM	#7
Serf27 Brigadier General 2851 Rep 4,322 Posts Drives: 335i Join Date: Apr 2018 Location: Sitting in a BMW. iTrader: (-1)	I hooked up bimmer geeks ProTool which is near the same as inpa for reading shadow codes isn’t it? No codes popped up at all. Besides transmission fluid quality.
	Appreciate 0 Quote

10-11-2019, 09:30 AM	#8
porsche959 Banned 471 Rep 996 Posts Drives: porsche Join Date: Jul 2018 Location: chicago iTrader: (0)	Spray some carb cleaner around the engine. If it revs up, you have a vacuum leak.
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10-11-2019, 11:54 AM	#9
NOKO Captain 253 Rep 731 Posts Drives: E91, E36M3, G05 Join Date: Nov 2017 Location: Berkeley, CA iTrader: (3) Garage List 1995 BMW M3 [0.00] [0.00]	I had this same issue and solved it by removing and cleaning the vanos solenoids. It's a really common problem since oil builds up in and around the solenoids. They are very easy to remove and clean and shouldn't take longer than 30min
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10-11-2019, 11:55 AM	#10
Fritzer No one sleep in Tokyo 945 Rep 1,507 Posts Drives: 2011 E90 328i//1995 E34 530i Join Date: Oct 2018 Location: San Diego, California -> Austin, Texas iTrader: (3)	Is your issue similar to this? https://www.e90post.com/forums/showthread.php?t=1601784 __________________ 2011 E90 328i, 1995 E34 530i, 1992 E32 740i, 1991 E34 525i
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04-02-2024, 10:59 PM	#11
HUMBLEN52 Registered 0 Rep 1 Posts Drives: 2010 BMW 528I XDRIVE Join Date: Apr 2024 Location: Ontario iTrader: (0)	Hey any luck with a fix for this issue? My 2010 528i xdrive E60 model is doing the same thing I can’t figure out what it could be, any help is appreciated
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04-05-2024, 12:03 AM	#13
Serf27 Brigadier General 2851 Rep 4,322 Posts Drives: 335i Join Date: Apr 2018 Location: Sitting in a BMW. iTrader: (-1)	I never figured it out. I cleaned the vanos solenoids once and the issue continued.
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