Rough idle stalling out… please help

[Mfg_m4]

Hey I have a 17 m4 and I just had it tuned yesterday along with downpipes, spark plugs, oil change, front mount intakes and charge pipes. I’m running the bm3 stage 2 ots map and today I went to cold start the it starts up to 2k rpm and then idles very rough between under 500 rpm and 1k rpm and then after like 5 seconds the car just stalling out and turns off. I then restart the car and it bounces around but stays alive and after about 10-15 seconds it is at steady rpm and ready to go. Car sounds like metal grinding to start up but it goes. I have no codes thrown on the car but can’t seem to figure out the issue. Please help!

[MineralWhiteF80]

Do you have the cold start feature turned off? or is still in the factory setting?

Suggest double checking the charge pipe and front mount intake install first. Make sure all clamps and everything are tight and secure to prevent having an air leak past the sensors in the intakes. If everything seems correct, try flashing the tune back to OEM factory tune and then restart the car and see what happens. Is there any change?

It is not unusual for a rough idle with a BMW OTS tune plus aftermarket intakes. It's just hard to know how severe your situation actually is. My BMW stage 1 on factory intakes and everything still hunts and stutters a little bit on cold start. I've also heard rumors of a lot of aftermarket intakes having a weak seal on the 'long' intake pipe where the small rubber hose comes off the intake pipe to the intake manifold causing an air leak.

[Mfg_m4]

Originally Posted by MineralWhiteF80

Do you have the cold start feature turned off? or is still in the factory setting?

Suggest double checking the charge pipe and front mount intake install first. Make sure all clamps and everything are tight and secure to prevent having an air leak past the sensors in the intakes. If everything seems correct, try flashing the tune back to OEM factory tune and then restart the car and see what happens. Is there any change?

It is not unusual for a rough idle with a BMW OTS tune plus aftermarket intakes. It's just hard to know how severe your situation actually is. My BMW stage 1 on factory intakes and everything still hunts and stutters a little bit on cold start. I've also heard rumors of a lot of aftermarket intakes having a weak seal on the 'long' intake pipe where the small rubber hose comes off the intake pipe to the intake manifold causing an air leak.

I brought the car back to the shop I go to and he double checked every clamp and sensor and said they looked all good. We also reset the adaptations. I have not tried flashing to stock and trying it then and reflashing from there. Also I was told that on stage 2 it auto turns cold start off and that there is no way to re-enable it. Is this true? Also should I wait a few days and then try the reflashing steps and hope that the car adapts or should I try that now? Thank you for the response.

[Info@mad-us.com]

Originally Posted by Mfg_m4

I brought the car back to the shop I go to and he double checked every clamp and sensor and said they looked all good. We also reset the adaptations. I have not tried flashing to stock and trying it then and reflashing from there. Also I was told that on stage 2 it auto turns cold start off and that there is no way to re-enable it. Is this true? Also should I wait a few days and then try the reflashing steps and hope that the car adapts or should I try that now? Thank you for the response.

You can definitely turn it back on. Not that it has anything to do with the issues you are having. Where are you located it deifnitely sounds like the shop did not install something correctly or left something loose/ unplugged.

[Mfg_m4]

Originally Posted by Info@mad-us.com

You can definitely turn it back on. Not that it has anything to do with the issues you are having. Where are you located it deifnitely sounds like the shop did not install something correctly or left something loose/ unplugged.

Sarasota florida. Shop that I go to is very creditable in the area so I have a lot of trust in his work but we can’t seem to figure this one out. I’m definitely no mechanic but from what I can see and reach all the screws in the clamps seem tight and the sensors all look and feel to be plugged in all the way.

[Mfg_m4]

Originally Posted by Info@mad-us.com

You can definitely turn it back on. Not that it has anything to do with the issues you are having. Where are you located it deifnitely sounds like the shop did not install something correctly or left something loose/ unplugged.

I want to try to turn the cold start back on since you said it’s possible but I don’t have the phone cord and I have to bring it back to the shop to pull up bootmod and he can’t seem to figure out how to turn it back on. Adapter has been shipped though.

[MineralWhiteF80]

I will say... im curious of people's situations who have catless downpipes and open air filters and OTS stage 2 tune having the same cold start characteristics because of the OTS tune. Wonder if you need a custom tune to play with fueling a little bit in that area of the table to keep the car happy.


If your car runs and idles after the cold start roughness is over, and also accelerates smoothly under boost while on the road, I would personally just wait until your smartphone adapter arrives and then do the BM3 tuning yourself.

Direction 1: If the car runs perfectly fine and accelerates normally, I would reflash back to the factory OEM tune and then see if there are any changes in the way the car behaves on cold start. Dont worry about resetting adaptations or how long you should wait between changing tunes, or anything like that.

Direction 2: If the car runs like garbage all the time and doesn't drive 'normal' on the street, then I would stop looking at the BM3 tune and start looking at more part installation since you had a lot of stuff changed and messed with at one time.

If you still can't figure it out, you can use the BM3 app to datalog some information and then you can post your datalogs up and have someone look for questionable sensor values.

The cold start isn't necessarily your problem, I only asked originally because if it was still in the factory ON position, your idle speed would be higher than if cold start feature was turned off, and that provides more data on your comment of it starts up to 2k rpm and then idles very rough between under 500 rpm and 1k rpm and then after like 5 seconds the car just stalling out and turns off.. I was expecting your cold start to be turned off if the engine does a quick rev up but then go down to around or just below 1000 rpm.

To turn the cold start feature back on, you go through the BM3 smartphone application and select the OTS stage 2 tune. In the stage 2 tune menu, you will see a little gear icon that allows you to adjust settings within the stage 2 tune. One of the sliders you can move will be for the cold start feature. Once you adjust the slider to the "OEM factory" cold start setting, save the changes, and then reflash the stage 2 tune.

[BitchinManWheels]

I had the same problem!
Short answer: spark plugs.
Not too long story: I have a '15 M4 DINAN stage 3, had the bmw authorized DINAN dealer pull the piggy back off, install flex fuel plugs then flash to DINAN's e85 tune (it sucks btw) last year.
Fast forward to this year, did down pipes, flex fuel sensor, and proper custom BM3 dyno tune. I told them the plugs were done and gapped to .021 (what I told bmw to gap them to) so don't worry about it.
They said it ran great, putting down 600hp/650ft/lbs at the wheels on e70.
Picked it up and it was idling rough, real rough. Did the little tap on the gas to crawl and it died. Restart, rough idle, tap to go in reverse, dies.
Then I go out for a test drive with the mechanic and it's cutting out around 5000rpm under hard acceleration.
They said drive around and do some data logs.
After talking with some car buddies who have WAY more experience with mods and tuning they said to pull the plugs.
I was slow and meticulous, took me 4 hours.
The gaps were all over the place!! AND some of the plugs came out with zero effort!
So, I gapped them properly, screwed back in (dry of course) and torqued to proper specs.
Now the car drives great!!!
F*ck the stealership!!! They said "we'll have our M guy do it". I should have had them check the plugs while installing downpipes…
Anyways, start with something easy like software reflash but I'm thinking spark plugs.
Good luck! Hope you get it fixed soon!

[Kilabyte]

^Came in to say plugs as well. Make sure they're gapped right, my cold start idle (I have cold start delete) was a bit rough when I had them gapped a tiny bit too tight.

[Mfg_m4]

Thanks for all the reply’s it really helps me out. I will try the software stuff first and then check hardware and then if I really have to I’ll check the spark plugs again. Just a pain. Thanks again for the help! I’ll keep updated.

[Mfg_m4]

Just wanted to update anyone having this problem. I reset adaptations which didn’t seem to do anything but I cleaned the airflow sensor in the intakes and that made it 95 percent better. Still a tiny tiny bit of bounce in rpm but it’s more 500 up to 700 and back so pretty solid. Since the filters come so oiled up from VRSF it got all on the sensors. Thanks for everyone’s help.