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Discussion Starter · #1 · (Edited)
I am running out of ideas on what to do next on resolving the P0171 and P0174 lean codes on my 2002 330Ci. (I would like to thank all who have had this issue before me for posting in forums everywhere...I have read them all it seems)

Here is the laundry list of things I have done:
Home made smoke test did turn up leaks
Intake leaks plugged
DISA O ring
Upper and lower intake boots
Intake gasket
Injectors professionally cleaned and flow tested with new O rings
O rings on the distribution pipe
CCV/Oil seperator and it's plumbing
Fuel filter
Vacuum line to fuel filter
Vacuum line from vacuum pump check valve to valve at back of manifold
Clean IAC
MAF Swap (Crappy one off ebay but still should work(waiting for the flame:evil:))
Air filter
Dip stick o-rings
IAT sensor
Fuel tank breather valve (had a different code for this)
Fuel pressure tested 50ish PSI
Intake vacuum tested 18ish mmHg
Oil filter housing seal (car had a bad oil leak for some time when I was told would cause the vacuum hoses to be in the condition they were in... mushy and falling apart)

Here are the items due to be replace:
Valve cover gasket (on hand)
Throttle body gasket (on order)
Air pump hose (not leaking but crusty)
Plumbing before the air box (on order)(was missing when I bought the car, could air from the engine compartment which is HOT and turbulent cause a MAF misreading )

Next steps (I guess):
Fuel pump
OEM MAF
DISA
 

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Discussion Starter · #3 · (Edited)
Here are my updates (no resolution to issue):

Valve cover gasket:Complete
Air pump hose:Complete
Plumbing before the air box:Complete
Test air pump and check valve:Complete pass

Next steps (I guess):
Throttle body gasket (have part)
Sucking jet pump (have part get to remove intake...AGAIN)

Smoke test exhaust?
Fuel pump
OEM MAF
DISA
 

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Instead of throwing a shopping cart full of parts at this car, why not just connect it to a diagnostic scanner -- the GT1 is excellent -- and let it tell you what the problem is?

You have two lean codes, one for each bank. Common parts to both banks of cylinders is the DISA and the MAF. You bought a "crappy" MAF (your own words), but don'[t seem to acknowledge that this could be the problem. A diagnostic scan will tell you what the problem is.
 

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Scan tools will not tell you what the problem is.

MAF is not the problem unless codes are triggered over 40 MPH unless MAF is not OE/OEM and mis reporting

My bet is your CCV lower oil return hose connected to the dipstick is broken.

See the first 2 links below in my signature for more info.

FYI, I have seen valve covers cracked cause lean codes as well.
 

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I had the same codes. I discovered the intake hose that goes from maf to the throttle body was cracked underneath. It was impossible to discover until I removed it and visually inspected for damage. Obviously this isn't necessarily your problem but is an easy and free thing to check.
 

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I believe in JFOJ's thread there is something to be said about soft fuel pump failure causing a lean condition. Does your car have any hesitation when driving? Running out of gas or laggy performance with 1/4 fuel left?
 

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Just pulled codes this morning, plan to check the intake once I get home today and worst comes to worst, I've seen that a lot of the time they go away with a new DISA. No hesitation while driving or running out of gas or lag in performance
 

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Check your Throttle Body Gasket + Idle Control Valve bent shaped gasket/gomment. Infact if they never been replaced, go ahead and replace them if you can, if anything it will at least help eliminate possibilities and you don't need to worry about them for 100k miles. I don't think its your issue from what your describing as a fuel system issue, if you are not having performance issue/lack of gas/throttle lag/hesitation. Also check to see if your vacuum hose to brake pump booster is not leaking or collapsed.

PS: A long shot but who knows, this might be your problem. Last time I had 174/171 code I realized the area around where the DISA valve inserts/intake manifold had mico-cracks in it due to the stress of me constantly prying out the unit with force. The crack don't actually open till the engine gets real hot and the plastic starts to expand a little. Even so, from what I can tell, the cracks was small enough to NOT cause performance/hesitation issues but just big enough to throw a code. Also explains why I didn't find them via smoke tests. Friggen drove me crack, must have went to Autozone/ORiellys to reset my dash a dozen times before I figured it out.

Hope this helps. What is a "jet sucking pump" btw?
 

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Discussion Starter · #11 · (Edited)
This issue has been resolved!!!

Work performed:
Throttle body gasket​
Sucking jet pump​
Result: FAIL :ben:

Work performed:
Buy wife a 2004 X5 with M54 :read:​
Swap MAF​
Result: PASS :clap:

Lesson learned (and don't say I told you so):
Don't buy MAFs from e-fricking-bay :banghead:​
 

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MAF is not the problem unless codes are triggered over 40 MPH unless MAF is not OE/OEM and mis reporting.
Seems to be a very common theme here with non OE/OEM MAF sensors. The ebay ones appear to be a big issue for some reason? They seem to to under report the proper amount of airflow and cause the engine to run lean.

What was the Gram per second reading at an idle with the ebay sensor installed?

This may yield some insight for others. Typical readings are in the 5-6 grams per second range as I recall?
 

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I don't know when it was triggered but I changed the intake air filter and oil filter and reset codes when I got my oil changed, hasn't come up yet. Might be something else but for now I'm in the clear. 118k and no rough idle and no lights on the dash. Loving my e46, as always haha.
 
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