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Discussion Starter · #1 ·
Just bought this car took it to the mechanic he said everything was fine..no leaks nothing..engine brakes, tranny is all good...just needed a alignment and new tires and brake fluid flush...

a week later..i get the service engine light...i take to autozone..got a P0174 BANK 2 RUNNING LEAN...??

could it be something major or just a dirty MAF sensor??..would rather do it myself if its simple instead of replacing a whole bunch of parts i dont need to only to find out it was something as simple as a O RING
 

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Under the lift arms
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13,172 Posts
I'm glad u recognise the fact that just throwing parts at a car is really bad, and down right ammature

But most of the time lean codes on almost all cars come from air bring sucked in after the map or maf,
Now Im not familiar with the 530 but I'm willing to put money on it that you a intake job maybe some hoses....... look for cracked hose's pipes elbows things like that......

And don't clean your maf, I'd fire you if I saw u doing that in my shop .... seems to be.a.regular thing here
 

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my first bmw
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Or try cleaning the intake. Seafoam?
Or reset the codes and see if it throws the code again.

Sent from my T-Mobile G1 using Bimmer App
 

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Discussion Starter · #6 ·
the car seems to run perfectly fine....it still runs as if the light never came on..im gong reset the light seee what ehappens...if it still gives me the light im going take in to my local bmw shop and get looked at

and i read and talked to alot of mechanics...the first thing people make a mistake on is thinking its the o2 sensors...so im not leaning towards that...a VAC LEAK..is more likly...but wouldn't that effect my gas milage and car performace??
 

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Entwicklung 39
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4,136 Posts
Intake bellows are probably leaking. That was the first thing my car needed..besides a new T-Stat and fuel filter.

Roll your windows down and accelerate slowly from a dead stop and you just might hear a slight whistling sound emanating from beneath the bonnet.
 

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It's a vac leak that plaging you--you have been given the info above that will help you in your quest. Check all of the spots and I would advise if you handy with a wrench to go a few extra steps with your new ride, change out the following. Vanos seals and valve cover gasket , CCV valve and the 4 hoses that go with it. I would be suspesious of you cooling system and would sugest that you renew it as well. If one part of the cooling system goes you could be in trouble. The cooling system parts usally start to go around 100k miles or so. If you were to do all of the above yourself, look to spend around 800 bucks in parts. If you take it to an indy, around 2 grand.
 

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check the rubber air boot just after the MAF, it becomes brittle and cracks after around 100k and will cause un-measured air inflow (along the unfiltered dust).
 

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03 540i now
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Was it cold when you started it? If so most likely vacum leak, mine was near throttle body. It would not leak when warm but on cold starts it would give the code 174 or 171 you really cant feel it in the motor unless you pay close attention. Clear the code and on the next cold start see if the code comes back during or right after the cold start. This was my experience hope it helps. With my symptoms on cold start I could feel but hear it better a slight miss in the engine. Or take it to a shop and do a smoke test.
 
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