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01 330ci 120k mi at a dead stop only or braking to come to a stop my idle will drop and lug the engine but it has never cut out completely the Rpms will go up and down slightly and then even out and idle fine and this is an automatic I've taken it in they say they fixed it it will work for at the most 2 weeks then the problem will start again it's probably been happening for around a year now but the past year I havent really driven it that much. Now that I'm commuting again to work I'd like this to get fixed permanently and again this problem will only occur as Im quickly braking or if I'm at a red light and the car isn't in motion so I don't know what it could possibly be any one else have a clue???
 

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Sounds like a vacuum leak, what did the shop fix exactly because it sounds like your losing vacuum pressure somewhere in the system. I would suggest starting with your lower intake boots. Just my two and a half cents worth...
 

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I forgot what exactly was since it was a long while ago but I did take it in for a vacuum leak which threw up my check engine light and gotthat fixed so I'm assuming he would have saw the other one by the diagnosis but also if it was another leak wouldn't it throw another code so my engine light comes on?
 

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Check your engine codes first (Always). Assuming you have had a tune-up, most(but not all) rough idle issues are a result of a vacuum leak. There are ton's of posts related to e46 rough idle issues and places to check/fix/replace (many culprits) and with DIY's. Best to go thru them all starting with the easy/cheapest to check/fix first.We have all been there. Good luck and let us know what you find.
 

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Most likely it is a vacuum leak, but not one that is not really that big. A forum member here had a big tear and his car would die when we put it in drive and tried to move it. If you don't know how to take out the intake track use my DIY vid

http://www.youtube.com/watch?v=STy-J10DtiU
 

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What did they do to fix it for two weeks?

Although vacuum leak is very common, I had your symptoms in my manual...see idle surging thread.

Opinions vary, and it may be because there are many ways to get a similar symptom.

Mine was fixed for maybe a year when my shop clean my icv and tb. It came back in a year and I went whole hog from the maf back and I've been trouble free since.

Forget when I did this, but you can check for my first post on 'icv grommet'

I cleaned maf, disa, icv, tb (by removing), replaced rubber where I could (disa, tb, icv grommet(probably unnecessary).

I dabbed rtv on the vac hose going to upper intake hose, replace lower intake hose, lubricated throttle cable (you probably don't have one).

I'm not saying this will fix your problem, but it did mine.

BTW, many know I'm kind of serious about cleaning...since I was also doing radiator at the time, I had time to do lots. I used a whole can on maf over a day, almost two cans with icv (figured it would be worth $10 not to go there again...dealer really won't clean; they'll replace. On icv, I turned it every way I could and sprayed from all orientations...except furrie.

Get the right cleaners for things.

This whole little expedition probably cost less than $100...much less I think.

Other thing I've heard associated with idle surging issues is the ccv, but I'm not quite sure I know why that is...or if it even is.

Oh, finally, on vac leak? I did not have a tear in my lower intake...just a loose hose to brake booster, but not really leaking badly at all. But, maybe that little bit was enough...though I doubt it.

That said, it might have been just my maf cleaning that fixed it...who knows, though I kind of doubt it.

Everyone will be there sooner or later.

If you have a nice shop, see if they can smoke the intake system for you. You can try with carb cleaner and you might get a rise from the engine...if so, you have a leak. Spray around on outside of intake...disa, around tb...though honestly, cleaning is always good even if it doesn't fix your issue!

Also, Techron and a high speed run in third to blow things out of the engine!
 
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