erratic rpm on cold start, video

akkando · 07-31-2020, 01:26 PM

For a while now the car seems to have erratic rpms on cold start only (car sitting for many hours). No codes, no limp mode, no stalls. TA never replaced but brass gears installed. Bounces around but never drops below 1k rpm for like ten seconds. Don't be alarmed at the weird noises at the end of the video, the trash cans were being dragged into the garage. Perfectly normal when it's not a cold start.

Fuel pressure sensor? idle control valve? When I installed the new plenum idle control valve tube connection isn't perfect on the plenum (probably my fault), but I don't think there is a leak but could be that?

akkando · 07-31-2020, 08:22 PM

Idle is rock solid when car is warm and full tank of gas so I am guessing not fuel breather valve.

akkando · 08-07-2020, 02:36 PM

Bump to see if anyone has any insight!

akkando · 01-16-2021, 09:58 AM

So I bought a battery charger and this weird cold start behavior went away after I fully charged the battery. Weird.

DL335D · 01-16-2021, 09:35 PM

Strange. I have the exact same type of jumpy idle. My battery is the original from 2013, but seems to be working as it should.

mapster37 · 01-17-2021, 05:11 AM

i had the exact same symptoms for a long time. finally one day i got fuel pump malfunction check control followed by check engine light. codes stored for fuel pressure sensor. i replaced the sensor and issue went away. hope this helps

Ajolives · 01-17-2021, 08:08 AM

All my (real) idle issues I've had were fuel-related.

I've also had issues when I didn't seat the plenum all the way and didn't seat the breather hose in the back. (Separate occasions)

There any codes at all? Smell fuel anywhere?

white_4door · 01-18-2021, 04:55 AM

if it goes away with charged battery i would suspect the battery is the issue. a lot of weird things start to happen when the battery is on its way out. check all grounds on valve covers and main engine ground underneath on driver side. other than that could be something with idle air valve

07-31-2020, 01:26 PM	#1
akkando Major General 5863 Rep 6,634 Posts Drives: 17 M2 DCT LBB,11 e90 M3 ZCP IB Join Date: Jan 2017 Location: Bay Area iTrader: (1)	erratic rpm on cold start, video For a while now the car seems to have erratic rpms on cold start only (car sitting for many hours). No codes, no limp mode, no stalls. TA never replaced but brass gears installed. Bounces around but never drops below 1k rpm for like ten seconds. Don't be alarmed at the weird noises at the end of the video, the trash cans were being dragged into the garage. Perfectly normal when it's not a cold start. Fuel pressure sensor? idle control valve? When I installed the new plenum idle control valve tube connection isn't perfect on the plenum (probably my fault), but I don't think there is a leak but could be that?
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07-31-2020, 08:22 PM	#2
akkando Major General 5863 Rep 6,634 Posts Drives: 17 M2 DCT LBB,11 e90 M3 ZCP IB Join Date: Jan 2017 Location: Bay Area iTrader: (1)	Idle is rock solid when car is warm and full tank of gas so I am guessing not fuel breather valve.
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08-07-2020, 02:36 PM	#3
akkando Major General 5863 Rep 6,634 Posts Drives: 17 M2 DCT LBB,11 e90 M3 ZCP IB Join Date: Jan 2017 Location: Bay Area iTrader: (1)	Bump to see if anyone has any insight!
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01-16-2021, 09:58 AM	#4
akkando Major General 5863 Rep 6,634 Posts Drives: 17 M2 DCT LBB,11 e90 M3 ZCP IB Join Date: Jan 2017 Location: Bay Area iTrader: (1)	So I bought a battery charger and this weird cold start behavior went away after I fully charged the battery. Weird.
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01-16-2021, 09:35 PM	#5
DL335D Captain 580 Rep 940 Posts Drives: 2013 e92 M3 Q4 Join Date: Apr 2014 Location: Boston iTrader: (2)	Strange. I have the exact same type of jumpy idle. My battery is the original from 2013, but seems to be working as it should. __________________ 2013 e92 M3 2011 X5 35d 2018 F80 M3 ZCP
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01-17-2021, 05:11 AM	#6
mapster37 Captain 357 Rep 922 Posts Drives: F80 Join Date: Sep 2018 Location: Davie iTrader: (2)	i had the exact same symptoms for a long time. finally one day i got fuel pump malfunction check control followed by check engine light. codes stored for fuel pressure sensor. i replaced the sensor and issue went away. hope this helps
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01-17-2021, 08:08 AM	#7
Ajolives Captain 922 Rep 933 Posts Drives: E90 M3 Join Date: Mar 2019 Location: Tampa iTrader: (0) Garage List 2019 Audi SQ5 [0.00] 2008 BMW M3 [0.00]	All my (real) idle issues I've had were fuel-related. I've also had issues when I didn't seat the plenum all the way and didn't seat the breather hose in the back. (Separate occasions) There any codes at all? Smell fuel anywhere?
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01-18-2021, 04:55 AM	#8
white_4door Private 23 Rep 66 Posts Drives: 11 alpine white e90 Join Date: Oct 2018 Location: phoenixville, pa iTrader: (1) Garage List 2001 bmw 540i [0.00] 2008 bmw 535i [0.00] 2008 bmw m3 [0.00] 2011 bmw m3 [0.00]	if it goes away with charged battery i would suspect the battery is the issue. a lot of weird things start to happen when the battery is on its way out. check all grounds on valve covers and main engine ground underneath on driver side. other than that could be something with idle air valve
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