F30POST
F30POST
2012-2015 BMW 3-Series and 4-Series Forum
BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read
BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > N47 and N57 Turbodiesel Engine / Drivetrain / Exhaust Modifications > Erratic MAF sensor reading
Extreme Powerhouse
Post Reply
 
Thread Tools Search this Thread
      01-23-2020, 03:48 PM   #1
Srobbo122
Registered
2
Rep
2
Posts

Drives: BMW 318D
Join Date: Dec 2017
Location: UK

iTrader: (0)

Erratic MAF sensor reading

Hi everyone,

Looking through some live data with my scan tool on my f30 2012 320D and came across flow rate for mass air flow sensor, the car was idling and the MAF sensor reading was going crazy. It goes up and down constantly, anywhere from 1 g/s to 18 g/s, it also jumps from a low number to a high number, there's no flow. This is all at idle, when driving the same jumping happens.

So I've cleaned the Maf, changed the maf, changed the air filters and still the same thing keeps happening.

Ever since I've owned the car its also felt sluggish compared to my 2010 318D.

Does anyone know if this MAF reading is normal?

Thanks!
Sam

Last edited by Srobbo122; 01-23-2020 at 04:01 PM..
Appreciate 0
      01-23-2020, 11:02 PM   #2
eugene89us
First Lieutenant
United_States
336
Rep
367
Posts

Drives: 2018 BMW 328d
Join Date: Dec 2017
Location: MS

iTrader: (0)

That would be strange. I would need to connect my scan tool and monitor. I have 328d, which is US equivalent of 320d. Will report back in a few days.
Appreciate 0
      01-24-2020, 05:06 AM   #3
RJR82
Private
16
Rep
59
Posts

Drives: Bmw 318d
Join Date: Jun 2019
Location: Wales

iTrader: (0)

try cleaning your MAP sensor
Appreciate 0
      01-24-2020, 07:31 AM   #4
Enabled
Lieutenant Colonel
1397
Rep
1,791
Posts

Drives: 328xd Wagon, M2 Competition
Join Date: Jun 2018
Location: Houston

iTrader: (0)

I would also try a different tool, or log with Testo (uses factory protocols) onto laptop in realtime
__________________
-2014 328d Wagon, 8HP. Self-tuned, 270hp/430ft-lbs.
-2019 M2 Competition MT, Alpine White. Self-tuned 560hp
-2016 Mini Cooper S, MT. Many plans.
Others:
-E36 328is. 2000 Z3 Roady. 2003 VW Jetta TDI Manual. Estoril Z3M Coupe.
Appreciate 0
      01-24-2020, 06:04 PM   #5
Srobbo122
Registered
2
Rep
2
Posts

Drives: BMW 318D
Join Date: Dec 2017
Location: UK

iTrader: (0)

Thanks for the replies everyone!

Thanks, eugene89us, looking forward to seeing what your readings are!

I tried cleaning the MAP today, although it was very dirty it still did not solve the issue

I hooked my other scan tool up today and I am getting the same erratic readings.
Appreciate 0
      01-25-2020, 06:58 AM   #6
RJR82
Private
16
Rep
59
Posts

Drives: Bmw 318d
Join Date: Jun 2019
Location: Wales

iTrader: (0)

bit of a shot in the dark, but could it poss be to do with a dodgy thermostat and/or coolant temp sensor, and the ecu is flicking bewtween closed/open loop because of wrong feedback from the sensor,
would have thought it throw engine light mind, but stranger things have happened!
Appreciate 1
      01-25-2020, 01:46 PM   #7
eugene89us
First Lieutenant
United_States
336
Rep
367
Posts

Drives: 2018 BMW 328d
Join Date: Dec 2017
Location: MS

iTrader: (0)

So my car has times when it goes into unstable idle. Still under warranty, but no codes and dealer (including BMW engineer) could not figure fault out. Below are graphs, both at idle. One with unstable idle (see my other posts on unstable idle, I have it on video) and one with stable idle. I think MAF and idle instability is a symptom, not the cause.
Attached Images
  
Appreciate 0
      02-04-2020, 06:09 AM   #8
speedbirdblack
Private
speedbirdblack's Avatar
Sri Lanka
15
Rep
66
Posts

Drives: f30 M-Sport
Join Date: Oct 2015
Location: Colombo

iTrader: (0)

Garage List
Quote:
Originally Posted by Srobbo122 View Post
Hi everyone,

Looking through some live data with my scan tool on my f30 2012 320D and came across flow rate for mass air flow sensor, the car was idling and the MAF sensor reading was going crazy. It goes up and down constantly, anywhere from 1 g/s to 18 g/s, it also jumps from a low number to a high number, there's no flow. This is all at idle, when driving the same jumping happens.

So I've cleaned the Maf, changed the maf, changed the air filters and still the same thing keeps happening.

Ever since I've owned the car its also felt sluggish compared to my 2010 318D.

Does anyone know if this MAF reading is normal?

Thanks!
Sam
I have the same issue in my 318d essentially the same engine MAF part numbers are the same. check engine light with code P0101 - Mass Air Flow Sensor Circuit Range/Performance.

I tried cleaning MAF for the first time and it went away and could feel the performance difference too.

Then cleaned the dirty MAP sensor too but after some time the code came back and itself cancels after a few runs. However, the car is awful to drive, gear shifts are horrible too.

cleaned the MAF again but no difference to the performance.
According to the scan tool MAF reading are flactuating at idle 1.5g/s to 16g/s

let me know if you have rectify the issue.
cheers
Appreciate 0
      09-21-2021, 03:41 AM   #9
lasseblomqvist
Registered
0
Rep
3
Posts

Drives: BMW 520D 2011 (F11)
Join Date: Sep 2021
Location: Sweden

iTrader: (0)

Hi everyone!

Did any of you ever find the root cause and/or a solution?

I see the exact same behaviour when I am reading my MAF values through an OBD reader. It is a different car model, F11 520D, but the same engine N47.
Appreciate 0
      09-21-2021, 08:52 AM   #10
andreigbs
Dr Drei
United_States
71
Rep
245
Posts

Drives: X3d
Join Date: Jan 2020
Location: WI

iTrader: (0)

Garage List
'16 X3d  [0.00]
Have any of you tried cleaning your EGR valves? I think a sticking EGR valve could also cause MAF numbers to be off.
__________________
GLK 250 // 126xxx miles // 36 MPG // Mobil1 ESP 5w30
Appreciate 0
      09-21-2021, 09:23 AM   #11
johnung
Major General
United_States
4511
Rep
5,377
Posts

Drives: 2015 BMW 335i x-Drive Auto
Join Date: Oct 2017
Location: New Jersey/Philadelphia

iTrader: (1)

Garage List
Quote:
Originally Posted by lasseblomqvist View Post
Hi everyone!

Did any of you ever find the root cause and/or a solution?

I see the exact same behaviour when I am reading my MAF values through an OBD reader. It is a different car model, F11 520D, but the same engine N47.
MAF symptoms can have multiple causes. Some guys were doing testing on several aftermarket intakes on another engine. They discovered that the intakes can change the stock environment of the stock MAF sensor with a different size or shape air pipe, different positioning of the sensor in the pipe airflow or obstructions in the pipe that change the airflow.

Performance gains from an intake upgrade are minimal (<5%) and can be had with a simple drop-in free flow airfilter such as aFe or K&N with no potential downside. If an aftermarket intake is desired for a sound increase, be aware that there is the potential for a poorly designed aftermarket intake to effect the MAF and possibly degrade performance.

IMO: MST seems to have an excellent combination of performance and sound increase.
Appreciate 0
      09-22-2021, 12:30 PM   #12
lasseblomqvist
Registered
0
Rep
3
Posts

Drives: BMW 520D 2011 (F11)
Join Date: Sep 2021
Location: Sweden

iTrader: (0)

Thanks for the responses.

Yes, I recently cleaned my EGR. Not that I had any problems with it, more as a precaution.

No modifications on the intake on my car, all stock and a quite new quality air filter.
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 11:22 AM.




f30post
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST