Thread: Name that part!
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Old 10-07-2012, 01:33 PM   #7
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Join Date: Apr 2010
Location: Murrieta, CA
Posts: 9,223
My Ride: '94 325iC & '00 323i
Originally Posted by bimmerks View Post
Hello everybody, long time listener(viewer), first time caller(poster). Well guys my 03' 325i is getting up there in mileage and its starting to show it. I'am currently dealing with the dreaded lean codes, misfires issues that i have been finding on posts. I took it upon myself to fix it myself rather then to get ripped off at the dealer or local mechanic. well after research i figured it was the CVV/Oil seperator issue (so i thought). i took my car apart and found out that lower boot was ripped and oil line to cvv was broken. i decided to replace the whole cvv unit while its bound to break soon. Anyways long story short i was taking parts out: icv,lower boot, cvv. i dont know when but a rubber cap fell in my hand from underneath. i didnt know what its for! i know there are 2 rubber vacuum caps behind the manifold near the firewall but this fell from under the manifold. can anybody tell me what this is for and if it going to cause issues, because i already put my car back together. anyways car still runs like crap and just made it home without breaking down. only thing i can think of next is fuel related. thank you in advance

ps. im still dealing with rough idle, and going from 9 codes up to 11! WTF

P1085,p0300(new),P1344,P1346,P1342,p1083,p0313(new),p1349,p1 351,p0174,p0171
Going from 9 to 11 codes is no big deal, relax. Many of your codes are all related to the same thing.


The MAF tells the computer information about the quality or the intake air, where "quality" is mostly temp and density. Air quality is important to know because the computer wants to crerate a 14.7:1 air/fuel ratio. If the air is cold and dense, then more fuel is needed. If the air is warm and thin then less fuel is needed. So far so good? If the actual air is cold and dense, but the MAF reports one second that it is warm and thin, then the fuel will be leaned out BY THE COMPUTER because it responds to the lies being told by the MAF. But the MAF is not content to tell the same lie for hours on end, and it wavers between lying and telling the truth. This results in the fuel mixture changing within a very wide range. The O2 Sensors monitor the exhaust gasses and feed information back to the computer, which trims the fuel delivery to try and acheive the mythical nirvanna of 14.7:1.

During the lean times (as determined by the MAF) the combustion cycle is weak, this causes the crankshaft to fail in getting from onen position to the next within a specified period of time, and the result of this is a MISFIRE code -- you have at least two codes that come from misfires. During the lean times, the O2 Sensors also report the lean condition and you have at least two lean codes, P0171 and P0174. So, here are four codes that come from the same part.

You need better diagnostic assistance -- a smarter diagnostic machine that can look with better clarity into the chaos that is your engine management data -- to see what the real problem is. I have not spent any time or effort to look at all of your codes, but several of them jump right out of my monitor as being related to the same thing. You do not have many problems, you have one or two problems that affect many different areas. That's my message. Good luck.

Last edited by jdstrickland; 10-07-2012 at 01:34 PM.
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