Bmw m5 f10 rpm hunting on cold starts

[AKRM2C]

Hi everyone. My car is an m5 f10 my 2012.

Started my car this morning, and soon after i noticed the car is hunting (rpm jumping up and down). But, severeal seconds later, it stabilizes itself (as seen on the video) and rpm is idling wonderfully. Attached video below.

https://youtube.com/shorts/g-i5T76CL...NtotVI2gwmqeia

Theres no vacuum leak (tested with smoke device). And theres no fault codes. Anyone suffered from such issue?

[M5_Raz]

Mine does it too from time to time, as many others to the point that I’d consider it on the normal side.

Some even shut off. I am usually ready to feather the gas pedal and keep it at 1k rpm until it calms down.

I did notice that when I tried a different gas brand, it was more minimal. My best guess is that it is due to bad gas.

[AKRM2C]

Update: i noticed the hunting of rpm only happens if the car is not used for over 2 days. If i use it daily. It hunts just a tiny bit.

Anyone knows what may be the issue? Thanks!

[KurtsM5]

Mine does it when it is cold. When it gets above 160 degrees it stops. I think it's DMEs' doing DME stuff.

[AKRM2C]

I live in a tropical country, where its mostly hot

[vafan13]

I'd start by cleaning the MAF sensors. CRC MAF cleaner is cheap and it's a quick thing to rule out.

[AKRM2C]

New mafs too, as i said, it happens only if the car is left for a while (2 days plus). If i drove it daily, never happen.. im confused🥲

[B58]

Mine does it too. I also notice when it does it my bank 1 LTFT are a bit higher than bank 2 and that’s when the O2’s also start adjusting. I have new MAF’s and all 4 oxygen sensors.

[AKRM2C]

Is this something to be alarmed? What to fix?

[M5Rick]

If there is no other recourse it's the fuel, storage tanks for fuel may have filters which may not have been changed and the fuel grade quality could be suspect.

[AKRM2C]

Hi, sorry can tou explain what you meant by “recourse”? thanks

[M5Rick]

Originally Posted by AKRM2C

Hi, sorry can tou explain what you meant by “recourse”? thanks

Sure . That means if all avenues have been searched by adjustments and parts replace then there can only be one possible culprit, the fuel.

Saying that you may have to check your own fuel tank and fuel filter for possible dirt/contamination.

[AKRM2C]

I see. Thanks M5Rick my appointment should be sometime next week. Will update soon!

[jpophammer]

Ok, I’ve been hunting for a cure to this. Did new plugs, coils, MAF’s. Still was “hunting”.

I found an old thread about resetting the throttle and it has seemed to work. If I let her sit for more than a few days it seems like I need to do the reset again.

Hope this helps!

Turn the car on but no engine. Press the gas to the floor for 5 seconds. While your foot is on the gas, turn the car off. Once off, obviously take your foot off the gas. Wait about 2 min for all the electronics to cycle off. Then fully restart. Should have a buttery smooth idle!

Best of luck and if anyone has a better idea or info, feel free to let me know!!!!!!

[M5Rick]

^It's worth trying anything that seems easier rather than doing the usual as you say with changing plugs, coils and the other things then finding there's no difference

[KurtsM5]

Try this. Let it sit for a couple of days, then rock the car body for a couple of minutes to shake the fuel around. Then start it. If no hunt then it sounds like some water settling to the bottom of the tank. Fuel pickup is in the bottom of the tank. Gas is lighter than water.

[M5Rick]

Originally Posted by KurtsM5

Try this. Let it sit for a couple of days, then rock the car body for a couple of minutes to shake the fuel around. Then start it. If no hunt then it sounds like some water settling to the bottom of the tank. Fuel pickup is in the bottom of the tank. Gas is lighter than water.

When I go to Poland sometimes I am advised to only use BP. One other brand which is even used for marketing in F1, was at the time suspected of adding water to their gas and people who gassed up with their product were complaining of sputtering and rough running in their vehicles.

[AKRM2C]

Update guys, have not get a schedule on ny workshop. Theyre packed😅. But someone told me about “unmetered air”, i re do all my intake clamps, and make sure its all seated properly, and voila, no more hunting on cold starts.

Ps. Very minor hunts is reported to be normal on these engines.

[AKRM2C]

Nevermind, its not fixed, waiting for my appointment with my shop next week

[quartz_m5]

Originally Posted by AKRM2C

Nevermind, its not fixed, waiting for my appointment with my shop next week

Having this same issue, what did the shop end up saying?

[AKRM2C]

No, but i compared to several other m5 and m6s most of them does it.

[AKRM2C]

Yeah BM3 stage 1 ots