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Old 03-02-2015, 04:20 PM   #1
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2003 E46 330 Lean Codes. Help!

Hi everyone,

First of all I am a newbie to these forums and I want to thank you all in advanced for any help I receive.

I have a 2003 330CI and I am getting lean codes and have a slight misfire. I have a full scanner that gives me all of the bmw codes but the only ones present are P0171 and P0174.

Now I replaced all of the vacuum lines so no vacuum leaks, the intake boots that always crack, the DISA valve, the PCV system is not bad, I have a new fuel pump and the fuel pressure is also good. I replaced the MAF and the oxygen sensors and still I keep getting the lean codes

The codes pops up within a few minutes of start up. The strange part is that when I disconnect the MAF the I no longer have a misfire and I no longer have lean codes, only the code for MAF because it is disconnected. When the MAF is connected I get a steady reading from the upstrem oxygen sensors of close to .07 V That is extremely lean When I disconnect the MAF I fluctuate between .2 to .8 which is about normal. I am stumped I don't know what to do because I've been trying fix this problem for months I need to pass inspection to renew my regi so I'm riding dirty now. Please give me some ideas. Do you think I may have an electrical issue? Thanks!
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Old 03-02-2015, 04:51 PM   #2
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I'd say it's either the ccv or valve cover gasket leaking. Best bet would be to do a smoke test since that will show where the vacuum leak is
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Old 03-02-2015, 05:14 PM   #3
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Hey firehawk, thanks for the reply. It doesn't seem like it because it runs perfect when the MAF is unplugged. I can also feel a big difference when I unplug the top ccv hose from the valve cover, the car really begins to misfire then and the idle is really rough. I will do a smoke test and see what happens.

Last edited by ZeusE46; 03-02-2015 at 05:14 PM. Reason: 1
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Old 03-02-2015, 07:23 PM   #4
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Disconnecting the MAF put the engine into an Richer fuel map that will mask or cover up a Lean condition. It is not a way to condemn a MAF.

FYI, a lower O2 Voltage is an indication of a Lean condition.

Need to see the warm idle Fuel Trim and any Freeze Frame data and EXACT OBDII trouble codes in Pxxxx format.

If you want to understand the difference between good and bad O2 sensors you should look at this - https://e46fanatics.com/forum/showpos...9&postcount=34

You need to read the first 2 links below in my signature.

Read this thread - https://forum.e46fanatics.com/showthread.php?t=1057387

Read my "BMW 20 Questions" comments in this thread - https://forum.e46fanatics.com/showthread.php?t=1059972

Search YouTube for Scotty Smoke Test. Do what Scotty does or build a tester from related video.
Solve your misfires, lean codes, rough idle - https://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - https://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - https://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - https://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose temp switch O-ring - BMW #13621743299
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Old 03-04-2015, 09:34 AM   #5
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Thank you guys for the help. I ended up changing the MAF sensor and resetting the codes and finally, no more lean codes :banana:

I finally got my inspection and renewed my regi. I had done a smoke test and all was good so I knew it wasn't vacuum related. I am just surprised that both bad MAF sensors did not show a MAF code.

Hope this helps some people with similar issues. Thanks again!
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330, lean codes, m54, p0171, p0174

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