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Discussion Starter #1
My car is exhibiting the cold start rough idle or idle hunting. It have stalled on me few times. There is no power under 2000 rpm going uphill until I pass 2000 rpm which acceleration power returns to normal. I live in hilly area which it makes this very noticeable every morning.

Does this mean I have air leak or vacuum leak somewhere under the plenum? I am planning on tackling on the valve cover gaskets to stop the oil from seeping out/increased oil consumption.

I will have to check the scan the ecu for the hidden codes because I haven't gotten any codes since that day I had a code for secondary air leak couple months ago.

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Discussion Starter #3 (Edited)
In the first video, I struggle to keep the rpm high enough without stalling when you first move M5.

I also want to mention that the idle speed causes the car to shake a bit. Right now, the car is already warmed up since my brother took it to gym this morning.

I also have 2 codes that are unrelated to this issue. Servotronik with speed plausibility and cruise control codes came up on INPA.
 

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Discussion Starter #4
So I did brake pumping test while idling, nothing were changed. It held steady idle.
 

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Discussion Starter #5
Anybody else have an idea? I did hear some whistling upon start up and idle.
 

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When you say that the car lacks power below 2K and is normal after 2K is that at the same throttle position? Have you checked the "sucked air", ICV and the throttle position measurements in INPA?

As far as your two codes, and seeing the brake, ABS and DSC trifecta, I would start looking for the faulted wheel speed sensor.
 

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So you only have the rough idle, idle hunting and occasional stalling after a cold start? When it's up to temp, it idles OK?

And is the low power below 2000 just when cold, just when hot, or both?
 

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Discussion Starter #8 (Edited)
So you only have the rough idle, idle hunting and occasional stalling after a cold start? When it's up to temp, it idles OK?

And is the low power below 2000 just when cold, just when hot, or both?
Yes I would have rough idle, idle hunting, and occasional stalling right after a cold start. When its warmed up, all these issues disappears.

Power is low under 2000 rpm only in cold mode.
 

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Discussion Starter #9 (Edited)
When you say that the car lacks power below 2K and is normal after 2K is that at the same throttle position? Have you checked the "sucked air", ICV and the throttle position measurements in INPA?

As far as your two codes, and seeing the brake, ABS and DSC trifecta, I would start looking for the faulted wheel speed sensor.
It is the abs module went out on me. DSC relay fault in GT1 software. It was still dead way before the timmayfest.

Yes to the first question about power using same throttle position. I have not checked the INPA since my battery is discharged on my window laptop. :dunno:
 

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Discussion Starter #10
So this morning, I started it up. The M5 struggled to keep the rpm steady. It went from 1200 rpm then to 500 rpm and back to 1200. It did this for 45 seconds roughly or so. I think it may have to do with secondary air system or vacuum leak under plenum. The engine felt like it will want to stall but catches, then raise the idle.
 

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Tunes can do this with the cold start. Mine is evolve tuned, and after a tune, I had this issue, contacted evolve and they fixed it with a new file base on my description of the symptoms.

Yours was tuned for how long, and did this just all of a sudden? Did you do some recent work under the hood and now this is happening?

Edit; also, can you replug your MAFs to see if that changes the symptom?
 

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So this morning, I started it up. The M5 struggled to keep the rpm steady. It went from 1200 rpm then to 500 rpm and back to 1200. It did this for 45 seconds roughly or so. I think it may have to do with secondary air system or vacuum leak under plenum. The engine felt like it will want to stall but catches, then raise the idle.
Does it coincide with the SAP running? In other words, does it smooth out when the pump stops?
 

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Discussion Starter #13 (Edited)
Does it coincide with the SAP running? In other words, does it smooth out when the pump stops?
Yes. It almost smooth out as soon as SAP stop pumping. I also deactivated the AA code as part of the tune. I have been trying to fix everything slowly before I got new file for my car.

I believe I have the tune since thanksgiving of last year. With MAFs or not, it does this. I once had the code with secondary air system leak detected but it never returned.
 

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Discussion Starter #15
Can you do logging with INPA during a cold start?
Yes I can. I just need to know how to do screenshots. Which analog do you want to see importantly?
 

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Yes I can. I just need to know how to do screenshots. Which analog do you want to see importantly?
To see what's happening, it's best to take a video of the time the idle is acting up. The trouble is both Analogue values 1 and 2 screens are useful, so it might take 2 cold starts. Go for the analogue 1 first. You can attach the mp4 file here or do the Facebook think which is quite straightforward.

I'm not promising I can do anything with the info! But it might provide a clue.
 

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how many times did you pump the brake pedal you have to pump it at least 15 times to check for a vacume leak you could have a lazy o2 also
 

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Discussion Starter #18
To see what's happening, it's best to take a video of the time the idle is acting up. The trouble is both Analogue values 1 and 2 screens are useful, so it might take 2 cold starts. Go for the analogue 1 first. You can attach the mp4 file here or do the Facebook think which is quite straightforward.

I'm not promising I can do anything with the info! But it might provide a clue.
I will do that tomorrow as my brother already took M5 to gym so no cold start for the rest of the day. I am going to see if I can find all vacuum and see if there are any leaks when I do valve cover gaskets in few hours as engine is cooling down for me to work on. I am cleaning ICV while I am in there.
 

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Discussion Starter #19
how many times did you pump the brake pedal you have to pump it at least 15 times to check for a vacume leak you could have a lazy o2 also
I replaced pre cat o2 sensors few weeks after thermostat replacement. I probably did like 10, but i will try again tomorrow morning.
 

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Discussion Starter #20 (Edited)
Here is a cold start using analog #1 most of the video. I just cleaned out the oil separators yesterday as the drain valve part were clogged. I am pretty sure this were causing high amount of oil being consumed into the motor. Plenum was very oily and throttle bodies had a bit of oil standing. I clean it up with cleaned towels around throttle bodies.

The second video shows the camshaft positions after cold start.

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