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Discussion Starter #1
Hello,
It's sad but true that I am from Austria, neighbour of Germany where our cars where produced and need to get help in an english forum :)
Actually, i have 2 problems that make me grey hairs already, and I am not sure if there is a Connection between them because the first came long before the second

The first one is that, especially after cold start, the engine changes the exhaust sound (not basically the rpm) in very hearable steps (jumps), it feels like something is regulating, but not smooth and it was not before.

When I drive berween 1500 and 2000 rpm, I can hear this also even when the engine is hot. Most people wouldnt hear it, but it was not before, so I think something is not ok.

The second problem is thet the car goes sometimes in limp mode ("engine power reduced,...")
When it is in limb mode, the sound jumps are not anymore.

When it goes in limb mode, ist ALWAYS in P500 mode + full throttle and more then 7.000 rpm. Its courious that the problem is ALWAyS: idle contriol unit; SMG CAN BUS OFF (CD8B)

It doesnt make sense because the idle Control Units are not used at full power and there are 2, but no specification which one it is

I checked and cleaned the throttle acturators already, but they seem to be ok , and I checked the wiring of the idle Control Units,

Can it be that one of them is defective and makes that unusual symptom?
And what can be the reason of the Sound jumps?

Thanks for your help in Advance
 

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Not sure on the limp mode, but for the idle undulation, my e63 M6 has always done this and had gotten worse and worse over the past years...only during the warm up cycle and then very faintly on warm restart (like starting back up after going into a store for a few minutes).

But, After doing my rod bearings and vanos line replacement recently it has almost totally gone away on the warm up cycle...made me nervous because it has never sounded this good on startup until now, lol. I know it had nothing to do with the actual rod bearings or vanos line change, but suspect it was either the bleed process for the vanos that is required when changing the vanos line, or possibly a bad vacuum connector on the plenum as I found a broken connector that may have been allowing air in. The connector was one of the two small ones between the plenums and the firewall...looked like someone before me didn’t know it was back there and tried to remove the plenum without disconnecting it.

I actually made a video series on doing the rod bearing job...you can see the vacuum line connector in the part 3 of 13 video on removing the plenums that was broken...below is a link for reference. The broken connector that was on mine is shown at the 11:20 time mark on the video.


Not sure which might have gotten rid of the strange cold start undulation, but the two items seem to make the most sense on things that could affect it. I guess any of the vacuum connectors could cause this too if that was the reason it was doing it (vacuum leak). If it was the vanos system that had some air trapped in it over the years, the vanos bleed would be what took care of it.
 

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Discussion Starter #4
Thanks a lot for the competent information. Is there a possibility to check for leaking vanos pipes except opening everything, so that they can be changed with same efforts? I have this annoying vanos sound that started with 30 tkm already, only when the oil is hot and around idle rpm:
Can it be occured by leaking vanos pipes?
 

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Sounds almost like there is air trapped in the Vanos unit. Mine did the same ironically also on bank 2 (my car had been sat for a few weeks though), the garage ran a Vanos bleed routine at my request and the noise has not returned since.
 

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When you guys had this around the Rev range you mention 1500-2000 when the pitch changes do you get a slight surging when driving (like slightly more power slightly less power all the time in the range especially when cold)
 

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Discussion Starter #10
@pyro225 yes, ist exactly this behavior you described, feels like slightly pulsating power (and exhaust sound) at constant throttle… but where dors it come from?
 

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Ok this has been driving me nuts - I have a tubi exhaust so hadn’t heard much from up front but defo noticed this - have you tried the bleeding yet?
 

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Discussion Starter #13
I need the bmw servive center to do the vanos bleeding, correct?
I just have the problem that the secundary pump doesnt start at cold engine, but this comes from the ECU, the hardware is ok. If I ground the responsible pin of the ECU, the pump starts...
Also a bit courious....
 

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Mine seems to do this as well on cold start. I noticed if I try and drive immediately up my street during cold start it is pretty jerky.....also increased by my sprint booster I'm sure (throttle response is more sensitive). So I just have been letting the car sit during cold start, for about 1 min and then drive off.....no issues with jerking when I do this. If it was a Vanos issues I would think I would still notice it after the cold start....but it only happens during cold start.
 

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Discussion Starter #15
If it would only while cold engine, I could live with that, but there is also some slightly pulsating power and exhaust sound in warm condition, and it was not when the car was new.
Interresting is that in "limp mode" ( when something was wrong), the sound/power pulsing is completley gone.
 

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Discussion Starter #16
I did the vanos bleeding and the sound that I showed in the youtobe link in the previous post was horrible louder while the procedure , but always and only bank 2.
Finally It did not have an effect to the sound jumps of exhaust noise. What I found in the vanos Test was that the inlet Valve of Bank 2 has 360mA (nearly double than bank 1) and much longer times than Bank 1.
I think, I will try to switch those valves with Bank 1 and see if the problem walks to Bank 1..
Do you think, a little bit blocked vanos valve can make those problems?
 

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hey eagle which version of limp mode do you get - 4k redline or 7k? i gave it some stick and was about 7.5k and got the limp with 7k redline...

starting to think this sound like the same problem... strange question - are you using the genuine spec oil bmw recommend? i normally do but about 2 months before this began my dash said 0.0 on the oil so i got some emergence 10w60 on a sunday which wasn't Castro it was mobil1 i am not saying this has caused it but oil and vanos...
 
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