RPM drops on idle

E92_TYLER · 02-17-2018, 11:16 AM

Quote:

Originally Posted by spazzyfry123

Mine ended up being the vent valve for the fuel tank that is found under the intake plenum.

Thanks for the results! Going to replace soon!

patrick smith · 03-21-2018, 06:57 PM

gotta love these forums, to find the same issue and have lots of opinions and thoughts on the same issues, so good.

SO i filled up my 2013 E92 the other day, and my car is mostly stock, 30k miles, never one issue. right after filling up, tank was down to about 20 miles until empty, pulling out of gas station and stopped at the light, idle drops and bounces up and down a few times. but never stalled. got home no problems. car sat for few days, but i took it out today around the block and no issues. drove fine and idled fine. so can i assume itll just come back and get worse? or fluke? should i make it a priority to replace the valve or can i drive it for time as is?
i guess if it gets worse then itll bother me enough to replace the valve. but if its an intermittent issue and its not hurting anything, then leave well enough alone..

thoughts?

drrust · 03-21-2018, 07:13 PM

Quote:

Originally Posted by patrick smith

gotta love these forums, to find the same issue and have lots of opinions and thoughts on the same issues, so good.

SO i filled up my 2013 E92 the other day, and my car is mostly stock, 30k miles, never one issue. right after filling up, tank was down to about 20 miles until empty, pulling out of gas station and stopped at the light, idle drops and bounces up and down a few times. but never stalled. got home no problems. car sat for few days, but i took it out today around the block and no issues. drove fine and idled fine. so can i assume itll just come back and get worse? or fluke? should i make it a priority to replace the valve or can i drive it for time as is?
i guess if it gets worse then itll bother me enough to replace the valve. but if its an intermittent issue and its not hurting anything, then leave well enough alone..

thoughts?

The 'classic' symptom is that it happens after a fill up. For me sometimes it just idled roughly others it stalled. Wait and see if it continues. When it gets too annoying, change the valve. The hardest part is getting the back hose off.

drrust · 03-21-2018, 07:15 PM

Double post

BOOF-M3 · 03-21-2018, 09:15 PM

Quote:

Originally Posted by patrick smith

gotta love these forums, to find the same issue and have lots of opinions and thoughts on the same issues, so good.

SO i filled up my 2013 E92 the other day, and my car is mostly stock, 30k miles, never one issue. right after filling up, tank was down to about 20 miles until empty, pulling out of gas station and stopped at the light, idle drops and bounces up and down a few times. but never stalled. got home no problems. car sat for few days, but i took it out today around the block and no issues. drove fine and idled fine. so can i assume itll just come back and get worse? or fluke? should i make it a priority to replace the valve or can i drive it for time as is?
i guess if it gets worse then itll bother me enough to replace the valve. but if its an intermittent issue and its not hurting anything, then leave well enough alone..

thoughts?

Just get it done, you will have loads of fun taking the plenum off and for $80 it's a reason to celebrate with a Stella afterward. drrust and other have said the rear clip is difficult to take off, mine came off in a snap. That was a pun.

kyrix1st · 03-22-2018, 06:16 AM

Mine turned out to be loose clamps for plenum (intermediate part from air filter to the big ass V8 intake.

E92_TYLER · 03-22-2018, 08:08 AM

Quote:

Originally Posted by kyrix1st

Mine turned out to be loose clamps for plenum (intermediate part from air filter to the big ass V8 intake.

Thanks for the update! Will check mine as well before i rip the intake off

E92_TYLER · 04-12-2018, 07:05 AM

[UPDATE]: Replaced fuel tank breather last night and still seems to do the same thing

Any further advice is helpful, let me know!

nycplumber · 07-10-2018, 05:50 PM

Quote:

Originally Posted by E92_TYLER

[UPDATE]: Replaced fuel tank breather last night and still seems to do the same thing

Any further advice is helpful, let me know!

Did you ever resolve the issue?

R3dliner · 07-11-2018, 09:58 AM

Wouldn't hurt to put in a bottle of Techron. Maybe a fluke but it happened to me once and after a bottle never returned.

E92_TYLER · 07-13-2018, 03:25 PM

Quote:

Originally Posted by nycplumber

Did you ever resolve the issue?

Negative

Hasnt been bad since its so fucking hot here i have the AC on blast when i drive it so it keeps the rpms up a bit.
I will try some techron!

nycplumber · 07-19-2018, 05:38 PM

Quote:

Originally Posted by E92_TYLER

Negative

Hasnt been bad since its so fucking hot here i have the AC on blast when i drive it so it keeps the rpms up a bit.
I will try some techron!

Did you do a smoke test on the the brake booster?

E92_TYLER · 07-26-2018, 11:37 AM

Quote:

Originally Posted by nycplumber

Did you do a smoke test on the the brake booster?

I have not but im pretty sure its a booster issue.

Logodude · 08-01-2018, 09:46 AM

My car does something very similar if I’m understand correctly. The idle with a/c on is Aprox. 750-800 rpm and when and when the a/c is off the idle drops to 550-600 rpm. This is completely normal behavior as the engine will spin slightly faster to spin the compressor more for optimal a/c cooling and to also compensate for the added electrical load on the engine.

The vibration with a/c off (550-600rpm) is from the engine as it’s is spinning slower and therefore more time between power strokes causing vibrations. This is more apparent in 4 cylinder engine vs our cars but it’s still noticeable.

After coming to a stop, the engine would target the idle speed higher in order to prevent the engine from lugging and slowing go down to 550-600rpm to make it as seem less as possible to the driver. When you take you foot off the brake, the car is antispating you accelerating so it will spin the engine faster to give the engine more responsiveness.

To me, this makes logical sense but I’m no engine tunner nor do have a background in this.

E92_TYLER · 08-02-2018, 11:28 AM

Quote:

Originally Posted by Logodude

My car does something very similar if I’m understand correctly. The idle with a/c on is Aprox. 750-800 rpm and when and when the a/c is off the idle drops to 550-600 rpm. This is completely normal behavior as the engine will spin slightly faster to spin the compressor more for optimal a/c cooling and to also compensate for the added electrical load on the engine.

The vibration with a/c off (550-600rpm) is from the engine as it’s is spinning slower and therefore more time between power strokes causing vibrations. This is more apparent in 4 cylinder engine vs our cars but it’s still noticeable.

After coming to a stop, the engine would target the idle speed higher in order to prevent the engine from lugging and slowing go down to 550-600rpm to make it as seem less as possible to the driver. When you take you foot off the brake, the car is antispating you accelerating so it will spin the engine faster to give the engine more responsiveness.

To me, this makes logical sense but I’m no engine tunner nor do have a background in this.

You are correct but i have driven other e92 m3s that dont have such a harsh vibration. Its very possible my engine mounts play apart in this as well. Engine mounts will be done soon so i will repost.

BRNDNSLVRA · 02-19-2020, 07:39 AM

Quote:

Originally Posted by SCL_///M3

Hi All,

This thing has been bugging me for quite some times now, that whenever I bring the car to a full stop and leave my foot on the brake, the RPM stays at around 750-800rpm for a second then starts to drop and settles at 500-550rpm, at which point I can feel a slight vibration through the steering wheel. If I lift my foot from the brake the PRM climbs back to 750-800rpm (will drop back to 500-550 when the brake is re-applied). The only time this does not happen is when I have the AC on.
I have brought the car to my dealership and the tech told me that they couldn't find anything wrong with it, as the car does not throw any error code nor did they find any error code when they scanned the ECU.
I believe the normal idle speed for e92 M3s should be around 750 rpm, right?
Has anyone else experienced the same symptom? Any solutions?
Btw, mine is a 2010 DCT. I have done the DCT software update back in 2011 (there was a recall on the software).
Also, do you guys usually leave your foot on the brake at stoplights?

Thanks.

Wow. This is my exact issue. Havent read through yet but hopefully somebody found a solution to it. Im convinced its the brake booster or a vacuum leak somewhere.

JP10 · 02-19-2020, 08:34 AM

Quote:

Originally Posted by 954MM

Wow. This is my exact issue. Havent read through yet but hopefully somebody found a solution to it. Im convinced its the brake booster or a vacuum leak somewhere.

I don't think it's an issue. Mine does the exact same. With no AC running and if I am just sitting at a light I idle around 550. When I press the clutch It'll jump to 750. Also if I were to be sitting there @ 550 with AC off and go to turn AC on RPMs will jump to 700ish. Maybe it is a problem, but my car has been the same for 2 years.

woody888 · 11-12-2021, 01:48 PM

Does anyone solve the issue?

djsilverjohnson · 11-12-2021, 06:27 PM

Quote:

Originally Posted by JP10

I don't think it's an issue. Mine does the exact same. With no AC running and if I am just sitting at a light I idle around 550. When I press the clutch It'll jump to 750. Also if I were to be sitting there @ 550 with AC off and go to turn AC on RPMs will jump to 700ish. Maybe it is a problem, but my car has been the same for 2 years.

If it only happens when pressing the brake, I would check the brake booster and associated vacuum lines.

Ajolives · 11-12-2021, 07:45 PM

Quote:

Originally Posted by JP10

Quote:

Originally Posted by 954MM

Wow. This is my exact issue. Havent read through yet but hopefully somebody found a solution to it. Im convinced its the brake booster or a vacuum leak somewhere.

I don't think it's an issue. Mine does the exact same. With no AC running and if I am just sitting at a light I idle around 550. When I press the clutch It'll jump to 750. Also if I were to be sitting there @ 550 with AC off and go to turn AC on RPMs will jump to 700ish. Maybe it is a problem, but my car has been the same for 2 years.

Mine does the same thing, A/C draws power and idle increases - totally normal.

woody888 · 11-17-2021, 02:23 AM

Quote:

Originally Posted by djsilverjohnson

Quote:

Originally Posted by JP10

I don't think it's an issue. Mine does the exact same. With no AC running and if I am just sitting at a light I idle around 550. When I press the clutch It'll jump to 750. Also if I were to be sitting there @ 550 with AC off and go to turn AC on RPMs will jump to 700ish. Maybe it is a problem, but my car has been the same for 2 years.

If it only happens when pressing the brake, I would check the brake booster and associated vacuum lines.

What if the brake boost and vaccum line are fine? I've checked then and the pressure is fine

woody888 · 11-17-2021, 02:26 AM

Quote:

Originally Posted by Ajolives

Quote:

Originally Posted by JP10

Quote:

Originally Posted by 954MM

Wow. This is my exact issue. Havent read through yet but hopefully somebody found a solution to it. Im convinced its the brake booster or a vacuum leak somewhere.

I don't think it's an issue. Mine does the exact same. With no AC running and if I am just sitting at a light I idle around 550. When I press the clutch It'll jump to 750. Also if I were to be sitting there @ 550 with AC off and go to turn AC on RPMs will jump to 700ish. Maybe it is a problem, but my car has been the same for 2 years.

Mine does the same thing, A/C draws power and idle increases - totally normal.

So, your idle will increase if you turn on AC? How about turning off? Would idle drop when you turn off AC?

03-21-2018, 06:57 PM	#134
patrick smith First Lieutenant 128 Rep 302 Posts Drives: 2018 M4 competition Join Date: Mar 2015 Location: SO CAL iTrader: (0)	gotta love these forums, to find the same issue and have lots of opinions and thoughts on the same issues, so good. SO i filled up my 2013 E92 the other day, and my car is mostly stock, 30k miles, never one issue. right after filling up, tank was down to about 20 miles until empty, pulling out of gas station and stopped at the light, idle drops and bounces up and down a few times. but never stalled. got home no problems. car sat for few days, but i took it out today around the block and no issues. drove fine and idled fine. so can i assume itll just come back and get worse? or fluke? should i make it a priority to replace the valve or can i drive it for time as is? i guess if it gets worse then itll bother me enough to replace the valve. but if its an intermittent issue and its not hurting anything, then leave well enough alone.. thoughts?
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03-21-2018, 07:15 PM	#136
drrust Captain 336 Rep 724 Posts Drives: E90 M3 DCT Sedan Join Date: Jun 2016 Location: Cincinnati iTrader: (0)	Double post
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03-22-2018, 06:16 AM	#138
kyrix1st Colonel 2360 Rep 2,360 Posts Drives: G87 M2; E92M3 MT&DCT; M3 euro Join Date: Sep 2014 Location: nyc iTrader: (0) Garage List 2004 BMW Z4 [0.00]	Mine turned out to be loose clamps for plenum (intermediate part from air filter to the big ass V8 intake. __________________ Pass me if you can.
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04-12-2018, 07:05 AM	#140
E92_TYLER Private First Class 76 Rep 161 Posts Drives: 2009 E92 M3 DCT AW Join Date: Mar 2016 Location: oklahoma iTrader: (0) Garage List 2009 BMW M3 [0.00]	[UPDATE]: Replaced fuel tank breather last night and still seems to do the same thing Any further advice is helpful, let me know! __________________ Current: 09' E92 M3 DCT Alpine white / Black Current: 13' F150 Fx4 -daily Past: 04' E55 AMG Fbo, 03' E46 M3 99' E36 M3, 92' 240 RB26 408whp rocketbunny 03' SVT Cobra 481whp, 89' Fox 5.0 lx notch
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07-11-2018, 09:58 AM	#142
R3dliner Lieutenant Colonel 935 Rep 1,930 Posts Drives: 18 M3 6MT Join Date: Mar 2016 Location: NYC iTrader: (5)	Wouldn't hurt to put in a bottle of Techron. Maybe a fluke but it happened to me once and after a bottle never returned.
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08-01-2018, 09:46 AM	#146
Logodude Private First Class 26 Rep 147 Posts Drives: 2012 M3 ZCP Join Date: Sep 2012 Location: El Paso, Texas iTrader: (1)	My car does something very similar if I’m understand correctly. The idle with a/c on is Aprox. 750-800 rpm and when and when the a/c is off the idle drops to 550-600 rpm. This is completely normal behavior as the engine will spin slightly faster to spin the compressor more for optimal a/c cooling and to also compensate for the added electrical load on the engine. The vibration with a/c off (550-600rpm) is from the engine as it’s is spinning slower and therefore more time between power strokes causing vibrations. This is more apparent in 4 cylinder engine vs our cars but it’s still noticeable. After coming to a stop, the engine would target the idle speed higher in order to prevent the engine from lugging and slowing go down to 550-600rpm to make it as seem less as possible to the driver. When you take you foot off the brake, the car is antispating you accelerating so it will spin the engine faster to give the engine more responsiveness. To me, this makes logical sense but I’m no engine tunner nor do have a background in this.
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11-12-2021, 01:48 PM	#150
woody888 Private First Class 55 Rep 195 Posts Drives: E92 & F80 M3 Join Date: Nov 2014 Location: CA iTrader: (0)	Does anyone solve the issue?
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