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Discussion Starter · #1 · (Edited)
Hoping for some good advice from you guys, I really don't know what to do about my idle problem.

The RPM is not fluxuating much in idle, but I can hear the engine running rough. When driving it seems fine, no power loss or anything, exept the RPM seems slow to come down when letting off the throttle, and when holding the clutch the engine sometimes dies if I have the MAF plugged in.
Sounds like a classic vacuum leak or something similar. I can also hear "knocking" (don't know the english term for it) in my intake when starting the engine cold. It lasts for maybe a minute or so, and I think I may have a leak on some of the fuel nozzels or something.

However, my intake-boot seems fine, no cracks or anything. When I spray some brake cleaner around in the engine bay, I can hear that the engine is responding, but I can't locate the leak. I'm thinking it could be the CCV, but the I've tried the oilfiller cap-trick, and I think I have sufficiant suction.
I've tried working MAF's, but no change. I don't have any warning lights in the dash either, and I don't have access to any diagnostics device.
The ICV seems clean btw.

I didn't have a intake gasket at hand when doing this, so I didn't remove the intake manifold, but I will in a couple of weeks when my mechanic-friend is availible. Any advise in what to look for when I take it off? Should I replace the CCV w/tubings anyway? If so, I can order it right away.

Any help/tips will be greatly appreciated! :)
 

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2016 340i xD 6-spd
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It sounds like you do have a leak given that it dies if your maf is unplugged and given it's responding to your spraying cleaner around.

You removed the lower intake boot? Did you clean the icv? You said it 'seemed' clean, but if you remove it and shake it, you might notice it sounds 'dead' and not 'bright' as in, metal on metal clinking...the sound of clean.

But, intake leak can come from anywhere on intake side...lower or upper boot, the hoses coming into the upper boot, the disa or the ccv.

You might have someone rev the engine while you try to isolate a hissing sound with a garden hose (5' long about) as a mechanic's stethoscope.

That, or just start changing things out. If you didn't remove the lower boot, that's the first place 'we' seem to get an intake leak from...but, I'll also say that mine would stall also and that a trip to TB fixed it for me. If you search the 'idle surging' thread (think it was NicB's) you'll find my post about what I did to fix it. ymmv, of course. Also, a local autoshop may have a scanner that they'll let you use for free.
 

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Discussion Starter · #3 ·
I've changed the the lower intake boot, because I thought it was the problem, but no changed, plus the one I took off was just as good as the one I replaced it with. The part was cheap, so I guess it dosn't matter that much tho.

I didn't remove the ICV for it's place, because I didn't think it was the problem at the time, and when I say "clean", I mean the intake of the ICV was clean. Maybe I should disassemble it and give it a shake?

But yeah, the engine is responding when sprayed, but I think the leak is somewhere underneath the intakemanifold, or maybe a crack in the manifold it self? Because I can't seem to find the leak anywhere else. I mean, I spray first, I hear the engine rev's, and I try to close it down further and further but it is without response. The think about gasses and I think it's getting anywhere no matter how accurate I try to be I guess.

But should i replace the CCV anyways, while I have the intake manifold up already? Is it an item the regulary needs to be changed out?
 

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ccv's fail a lot, but again, leaks can come from a variety of places...and although you may have one in the ccv (my hose from VC to ccv valve had cracked...gets brittle with age), it might be from a number of little sources too.

But, the stalling is a tough one just coz guys have different results when doing everything down to TB...cleaning disa, icv, tb, replacing rubber behind. Worked for me is all I can say. Also, I guess you cleaned your maf? If not, get maf cleaner...not parts cleaner. And, if you need a new one, see if the Hyundai maf will work for you as it'd be a lot cheaper.

If removing the intake runner, there are 6 0-rings that you could replace...and probably worthwhile to do since they cost nothing and you won't be there again for a long time...I hope.

CCV isn't fun, but it's not horrible. Some need to remove the intake manifold to get to it...but since yours is off...the getting is good now. You mean the intake manifold, right? Not just the intake runner? Also, given your location, you should probably get the cold climate version ccv, and for that, many find they 'need' to remove mani.
 

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Discussion Starter · #6 ·
Thanks guys, I like this forum! :)

The intake manifold is not disassembled now, but it will be in two weeks, I just really hope this isn't going to be too expensive! :/

The stalling come when the MAF is plugged in to the system, and not when it's unplugged from the system. One of my friends thought that was strange, shouldn't the car go into emergency-mode or something, if I unplug it I mean? He thought so, so he also reckoned I just buy a new MAF, but wait until we find, if we find, anymore leaks.
 

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Thanks guys, I like this forum! :)

The intake manifold is not disassembled now, but it will be in two weeks, I just really hope this isn't going to be too expensive! :/

The stalling come when the MAF is plugged in to the system, and not when it's unplugged from the system. One of my friends thought that was strange, shouldn't the car go into emergency-mode or something, if I unplug it I mean? He thought so, so he also reckoned I just buy a new MAF, but wait until we find, if we find, anymore leaks.
Since your maf is dirty or failed otherwise, the signals were erratic yet evidently still within some reasonable range and the car was doing the best it could but being weird. By disconnecting the maf, you trigger it entering a 'mode' where it uses a factory default setting that it reckons will keep the car running...not efficiently for most driving.

Shanneba has posted about maf before with good info...also, search for Hyundai mafs here...might work on your car and be less expensive than bmw maf...and not much point in a used or aftermarket one...don't goof with our cars fundamentals, especially electronics!
 

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Discussion Starter · #8 ·
I agree, I won't goof around with it, I just don't want to spend money on things that isn't broken, that's all. I love my car to death, that's why I asked you guys for help! :)

I will def try for an Hyundai maf. If not, is there any other car with this type of maf?
 

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I agree, I won't goof around with it, I just don't want to spend money on things that isn't broken, that's all. I love my car to death, that's why I asked you guys for help! :)

I will def try for an Hyundai maf. If not, is there any other car with this type of maf?
Well, first...I forget...you did clean maf? If not, start there...and look for intake leak...and if oiled air filter, get rid of it.
 

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Discussion Starter · #11 ·
So I finally figured it out, it turns out the "rubber membrane" (not sure of the english term for it), in the CCV was cracked an ruined. I changed the CCV, cleaned all the things I think was relevant, and the car runs like it should.

But, this job, omg what a PIA! It took me two days, with approx. 5 hours each day, because I struggled to get the fuelrail leak-free, I forgot a couple of connections along the reassembly of the intakemanifold, so I had to disassemble things again, I've searched the web for solutions and so on.

I guess you learn by doing, and I've learned a lesson or two now. Anyways, the car is perfect now, and I hope it'll stay that way for a loooong time. (knock on wood) :)

Thanks for the help guys! :)
 
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