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16 Posts
Discussion Starter · #1 ·
Hi all,

I have a custom built E46 M3, we are facing an issue which we could not solve yet, and we are running out of ideas. The problem started with a hesitation during acceleration, it is more noticeable in higher gears, e.g.: pull in 5th gear, but I can feel it in 3rd gear, and even in 2nd, it's getting worse I think. Hesitation = the car does not pull linearly.

This problem started around 2020-06. I usually check my car with INPA every now and then, there were no error codes in that time.

The first guess was the ignition coils, they were not replaced when the engine was "rebuilt", so we ordered Bosch ignition coils and replaced them. The issue remained. We also replaced the fuel filter in this session, and we also did a compression test.

The second guess was the fuel pump, we did not measure the fuel pressure, we replaced the fuel pump with a Walbro GST400-003 (400 l/h), in that period the issue was seemingly resolved. But I remember that before the fuel pump replacement it was good for period of time, so maybe just some other factor played with us.

The first error code appeared in 2021-01 #230 EGAS-Soll-Ist-Vergleich (EGAS target / actual comparison) (error frequency 41, logistic counter 22), browsing some forums I suspected the TPS sensors. This error code appeared only 2 times and I have never seen it again.

The second error code appeared in 2021-04 #175 Kraftstoffsystem Diagnose 2, the live data showed bad values on adaptation value additive 1 and 2 (130 instead of the max 100). I accidentally cleared the adaptations with INPA, and the car stalled many times, the error codes that appeared in this period were: #170 Sekundärluft Mindestdurchfluss (Secondary air minimum flow), #144 Lambda Regler 1 (Lambda Rules), #145 Lambda Regler 2, #175 Kraftstoffsystem Diagnose (Fuel system diagnosis) 2.

We replaced the MSS54 ECU (2003 UK version) with a MSS54HP (2005 US version) for different reasons, and updated the firmware on it with EU4 software. This change is hopefully unrelated, just wanted to give a full picture. This introduced an error #1 Relais Kraftstoffpumpe (Fuel pump relay) that we can ignore as far as I know. I had the #174, #175 error codes this time only.

We went on with my TPS sensor guess, and we also got a used throttle actuator with a used TPS sensor. The funny thing: one of my old TPS sensors was indeed "bad", when I tried to replace it with the other it introduced some strange behavior, even misfires and the car could not keep the speed properly on cruise control. So we ordered new TPS sensors and replaced them. By the way the VANOS test, the EDK test (I don't remember the test name in ISTA, the throttle actuator test) ran OK every time we tested them.

Next, we replaced the pre-cat O2 sensors (Bosch). We also tried 3 different OEM MAF sensors (used ones), but neither did solve the hesitation. Now I have the "check" engine light on all the time, as far as I remember the check engine light came on before the MSS54 ecu change maybe one time only, after it was more common. Basically now I have it always on.

I just got back my OBDLink LX adapter, and I started to read about fuel trims. My error codes are P0171 and P0174. In INPA I saw a new one #77 Ansauglufttemperaturfühler (Intake air temperature sensor) I cleared that and never came back.

One more thing to add: there is an interesting vibration above 7500 RPM, no idea what causes that.

OBDLink CSV logs (cold idle, cruising, warm idle, screenshots on freeze frame) (how-to)

* LTFT are -24% and -25% (== inpa adaptation values 130?)
* 8-10 g/s on MAF

In summary what we have already tried:
1. Bosch ignition coils.
2. Walbro GST400-003 Fuel pump
3. Fuel filter
4. MSS54HP from the US with EU4 firmware. It has nothing to do with the problem, but it could be important somehow.
5. Used throttle actuator
6. TPS sensors
7. Bosch O2 sensors (pre-cat)
8. 3 different used OEM MAF sensors.

Just a note for my future self: there is one MAF sensor, six coils, six injectors, two knock sensors, two camshaft position sensors, and two pre-cat O2 sensors.

What should we do next?
- disconnect the MAF sensors and try accelerate
- fuel pressure test
- check for vacuum leaks
- debug knock sensors
- debug camshaft position sensors
- replace spark plugs? (they were nice when we looked at them, but could be soft fail without misfires?)
- give up and salvage the car
The hesitation and these lean codes are connected, aren't they? Just to make sure.

My answers for the BMW 20 Questions:

1. Have the spark plugs been changed and when?

Yes, 2018-10 (30k km since then).

Coils were replaced (Bosch) in 2020-09. (<5k km since then).

2. Has the fuel filter been changed and when?

Yes, 2020-09 (<5k km since then).

3. Has the air filter been changed and when? If the air filter was changed, is it an OEM style or K&N type of filter?

Yes. OEM style, 2021-02 (<3k km since then).

4. Have the intake boots been replaced and when?


5. Has the CCV and hoses been replaced and when?


6. Has the DISA been inspected or replaced and/or DISA O-ring been replaced and when?


7. Have the SAP vacuum hoses been replaced and when?


8. Have the O2 sensors been replaced and when?

Yes, Bosch, 2021-06. (<1k km since then),

9. Has the valve cover gasket been replaced and when?


10. Has the fuel pump been changed and when?

Yes, WALBRO BMW E46 inc M3 Fuel Pump Kit 400 ltr/h (Competition) GST400-003, 2020-10. (<5k km since then).

11. Has the dipstick tube and the dipstick O-rings been replaced and when?

Probably during the rebuild.

12. Have the air distribution manifold O-rings been replaced and when?

Probably during the rebuild.

13. Has the oil fill cap been replaced and when?


14. Has the power brake booster been replaced and when?


15. Has the IAT or IAT dummy plug O-ring been replaced and when?


16. Have the fuel injectors ever been sent out of for proper cleaning, flow testing and replacment O-rings and when?


17. Has the ICV been removed, cleaned and the ICV grommet been replaced and when?


18. Has the throttle body been removed, cleaned and the gasket been replaced and when?

Probably during the rebuild. The throttle actuator was replaced with a used one, brand new TPS sensors.

19. Has the fuel filter vacuum hose under the car been inspected/replaced and when?


20. Has the MAF ever been replaced and when? What brand was used to replace it and how much did it cost?

Nope, but we have tried 3 different MAFs.

16 Posts
Discussion Starter · #3 · (Edited)
I replaced the vent hose (11-15-7-831-311 hose between oil separator and air filter) that I identified with the smoke machine. I did not reset the adaptation values in INPA at first, during the test drive the hesitation still occurred. The smoke machine is not with me right now, but I will do a smoke test in the weekend. Today I reset the adaptation values and test drove it. The acceleration seemed linear to me, I did only 5-6 pulls so I am not 100% percent sure that the issue is fixed, but it feels like progress :).

The lean codes P0171 and P0174 are not yet back, but the short term fuel trims were -30% on both banks during warm idle. The long term fuel trims are currently zero (because I reset them). Before the reset and the hose replacement ,the long term fuel trims were -25%, I guess they will adapt back to -25%, so something must be utterly wrong here. I use the OBDLink android application for the logs, by the way INPA showed positive 130 values on live data (on the adaptation value 1 and 2, I guess those are the long term fuel trims, they could go to negative values according to the labels). The air mass flow rate on warm idle is around 8 g/s, is that normal?

As far as my understanding goes, running lean would mean positive fuel trims, but I always had negative fuel trims and lean error codes. So I am a bit confused here. Could someone look into the data logs the old ones and the new one that I just created? I would really appreciate it.



A new one: P0101 (maybe because the adaptation reset, the engine stalled multiple times)


Just out of curiosity, would a burble tune contribute to negative fuel trims?

16 Posts
Discussion Starter · #5 ·

This was in my car:
Bosch 0 280 218 062
7 830 359
385 27 3 A


This is an OEM one (production date 2012):
13 62 7 839 014
0 280 218 062
7 839 014
105 25 3 G (C?)

I replaced it and reset the adaptation values. There were no stalls (maybe 1 or 2), so I thought this will solve my problem (with the old MAF there were loads of stalls after reset), but unfortunately there is still something wrong. When I replaced that vent hose and reset the adaptation values my car was accelerating so smoothly for two days (with the old MAF). However, the MAF readings seemed odd and eventually my LTFT went to -25% on both banks.

Now, with the new MAF my readings are still looks odd compared the information I could search on forums. my LTFTs are back to -25% again, lean codes are in pending state. I told in my first post that we have tried 3 different MAF sensors, we did not have data logs back then, so that wasn't too scientific (I am still learning this stuff).

Warm idle with new MAF

What should be the correct values for a warm idle for an S54B32? According to this blogpost his faulty MAF reading were 26 kg/h (7.2 g/s) the correct ones were 18 kg/h (5 g/s).
According to this forum M54B30 idle at 750 RPM should be around 4 g/s as well, M52TU 28i at 750 RPM should be around 3.5 g/s. Around 1000 RPM they were both reading ~5 g/s.

My readings:
870 RPM 7 g/s (26 kg/h)
1500 RPM 10.5 g/s
3000 RPM 23 g/s

1. Could someone with an S54B32 check the MAF live data with OBDFusion or INPA or whatever, and share with me? I literally searched for hours and I could not see a table like they did for the M54B30. I think this would be really helpful for others as well.
2. What could contribute to high MAF readings?
3. The production date is 2012 on this new sensor, could this be bad as well? (I don't think so)
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