[carchrism5]

Car is a 2016 M2 BM3 Stage 2 91oct (about 5k miles) and 60k on the car. Plugs were changed two months ago.

Starting a few weeks ago on the first start of the day I noticed the car stumble, where the revs would drop to almost 500 RPM, then catch back up. Car would run fine otherwise. This only happened on the first start of the day, every subsequent start was fine.

Normal bits to check with starting are power, spark and fuel. Battery was tested and checks out fine, spark plugs are pretty new and I ran logs that I sent to BM3 to see if they saw anything and they said logs were all great.

One day it actually did stall out and shut off but started right back up. That was early June, then I drove the car and ran another tank of gas through it and it seemed to be quite a bit better. Then I got gas again yesterday and had the stumble this morning. Part of me wonders if there's any truth to the summer gas that is changed over by June 1 and I think the most noticeable stumbles were after gassing up at the same Shell station (93 V power, newer station).

A search of this yielded a number of results, many on the M2335 boards even with similar videos. Some people said it was sporadic, experienced it a few times then went away, a few under warranty claimed fuel pumps were replaced but that didn't seem to be the actual solution.

I haven't ruled out bad gas but curious if any others experienced this, thoughts on it or recommendations of other items to check.

Thanks in advance.

[ZM2]

How long does the car sit between morning starts? Any idea of the % ethanol content in your fuel?

I have a similar first start stumble, but I run E50 and my car might sit for a week bn starts.

[EDWYER]

Probably bad gas.

[XutvJet]

I had this EXACT thing happen on my M235 recently. The fix was simple. On a warm motor, turn the car off, open the hood, and then wait 10 minutes. After 10 minutes, disconnect the MAF sensor by the airbox and then start the car. Let it run 10 minutes and then shut it off. Reconnect the MAF.

I'm not sure why these cars do this but it seems to be a mild tuning glitch that doesn't throw a code.

Like you, my battery was fine, my plugs were newer and OEM with the stock gap, and I run a quality 93 octane fuel. I'm not one to throw parts at the car like most BMW techs have done to remedy this issue. The fact that this only happens on a stone cold start and the car runs completely fine otherwise points to a tuning issue and not a hardware issue like the HPFP.

[ZM2]

Originally Posted by XutvJet

I had this EXACT thing happen on my M235 recently. The fix was simple. On a warm motor, turn the car off, open the hood, and then wait 10 minutes. After 10 minutes, disconnect the MAF sensor by the airbox and then start the car. Let it run 10 minutes and then shut it off. Reconnect the MAF.

I'm not sure why these cars do this but it seems to be a mild tuning glitch that doesn't throw a code.

Like you, my battery was fine, my plugs were newer and OEM with the stock gap, and I run a quality 93 octane fuel. I'm not one to throw parts at the car like most BMW techs have done to remedy this issue. The fact that this only happens on a stone cold start and the car runs completely fine otherwise points to a tuning issue and not a hardware issue like the HPFP.

Does resetting adaptations do something similar?

[carchrism5]

Originally Posted by ZM2

How long does the car sit between morning starts? Any idea of the % ethanol content in your fuel?

I have a similar first start stumble, but I run E50 and my car might sit for a week bn starts.

This happened after sitting for 1 day.

Originally Posted by TooSoonJunior

Probably bad gas.

My hope

Originally Posted by XutvJet

I had this EXACT thing happen on my M235 recently. The fix was simple. On a warm motor, turn the car off, open the hood, and then wait 10 minutes. After 10 minutes, disconnect the MAF sensor by the airbox and then start the car. Let it run 10 minutes and then shut it off. Reconnect the MAF.

I'm not sure why these cars do this but it seems to be a mild tuning glitch that doesn't throw a code.

Like you, my battery was fine, my plugs were newer and OEM with the stock gap, and I run a quality 93 octane fuel. I'm not one to throw parts at the car like most BMW techs have done to remedy this issue. The fact that this only happens on a stone cold start and the car runs completely fine otherwise points to a tuning issue and not a hardware issue like the HPFP.

I actually saw that post and tried that as well. If I get another stumble I'll try it again since I did disconnect my battery to install my steering wheel recently.

Thanks for all the input.

[XutvJet]

Originally Posted by ZM2

Does resetting adaptations do something similar?

I have no idea. I can't reset DME adaptions. I can reset throttle adaptions but everything points to this being a weird air intake/MAF issue. Un and reconnecting the MAF was my fix as well as a couple of other M235s. Given that the N55 and tuning used in OG M2 and M235 are very similar and the issues the same, I'd start with the MAF first.

It wasn't fuel with my M235 because I tried two different brands and stations with no fix. My cold starting issue lasted 6 weeks and got progressively worse to where it was happening on every cold start. I did the MAF dance and the issue instantly fixed on the next cold start. That was over 6 weeks ago now and not a single issue since.

I do find it odd that you can disconnect the MAF on a hot N55 engine and it won't throw a code and run weird. I've never had another car be able to do that. I guess the fact that the motor relies largely on MAP is why.

[carchrism5]

Originally Posted by XutvJet

I have no idea. I can't reset DME adaptions. I can reset throttle adaptions but everything points to this being a weird air intake/MAF issue. Un and reconnecting the MAF was my fix as well as a couple of other M235s. Given that the N55 and tuning used in OG M2 and M235 are very similar and the issues the same, I'd start with the MAF first.

It wasn't fuel with my M235 because I tried two different brands and stations with no fix. My cold starting issue lasted 6 weeks and got progressively worse to where it was happening on every cold start. I did the MAF dance and the issue instantly fixed on the next cold start. That was over 6 weeks ago now and not a single issue since.

I do find it odd that you can disconnect the MAF on a hot N55 engine and it won't throw a code and run weird. I've never had another car be able to do that. I guess the fact that the motor relies largely on MAP is why.

I'll try again and see what happens. It does throw a soft code though, I scanned after I did it.

[F87source]

Do you have an aftermarket intake? This sounds alot like intake related issues, when I had an aftermarket intake on my m235i it would stumble alot and have terrible idles and that was due to the intake allowing a different flow pattern or more air past the maf housing causing stubmles.


Also clean your maf sensor, that can help if it is maf related.

[carchrism5]

Originally Posted by F87source

Do you have an aftermarket intake? This sounds alot like intake related issues, when I had an aftermarket intake on my m235i it would stumble alot and have terrible idles and that was due to the intake allowing a different flow pattern or more air past the maf housing causing stubmles.


Also clean your maf sensor, that can help if it is maf related.

Stock intake, but this did come up after replacing the air filter with a new one. Just standard filter though. Will clean the MAF as well, thanks.

[F87source]

Originally Posted by carchrism5

Stock intake, but this did come up after replacing the air filter with a new one. Just standard filter though. Will clean the MAF as well, thanks.

Make sure you use maf cleaner and be careful, mafs are sensitive and break easily.

[carchrism5]

Update: Ran the tank down and filled up with 93 from another station and it made a noticeable improvement. Wanted to try that first and take note, but will still clean the MAF.

[mikeyryap]

2018 F87 BMW M2

Hello, I am currently getting this issue and I need some help. I had low idles / stalls when in park and low RPMs. I did the MAF trick and it worked for a day but then the issue came back. I also recently got a CEL from “slow response” from my o2 sensor and this could be from my sensor spacers or MAF flow sensor. Any advice is appreciated. I’m thinking since it came back after doing the MAF unplug trick it could mean I need to replace the MAF sensor itself.