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Old 03-27-2014, 02:45 PM   #1
TFT
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325i P0171 & P0174 Blues

Sadly my first post is to seek help with the notorious lean codes. I have a new to me 2004 325i with 96k miles. The previous owner had stored it for the last 2 years, it was driven only a couple hundred miles during that time. It came with the SES light on with stored codes P0171, P0174, and P2197. The parts store cleared the codes and within a day P0171 and P0174 came back but I have not seen P2197 again.

The car runs and drives well, no starting or idling issues so far. It seems to have good acceleration and no hesitation. I had 360 miles on the last tank when the low fuel light came on, so decent MPG's.

I've since purchased the Torque pro app and have started to investigate the lean codes. I have so far been following Jfoj's excellent thread and trying some of his recommendations. Here what I've done so far;

-New battery (old one was completely dead)
-oil change

-techron fuel system cleaner 20 gal bottle, on second consecutive tank
-new fuel filter
-new fuel filter vac line
-checked CCV hoses, none are broken or leaking
-re-torqued valve cover no obvious leaks
-checked DISA and replaced o-ring , it was still functional and no rattle
-removed upper and lower boot, both were pliable with no cracks reinstalled
-cleaned throttle body, wasn't very dirty
-inspected ICV, it was clean inside no carbon
-cleaned MAF

I still have high fuel trims and both P0171 and P0174 codes.

Here is some of the data I've collected

Freeze Frame after last SES;

Fuel Status = 0 byte
Engine Load = 42.745 %
Engine Coolant Temperature = 201.2 °F
Fuel Trim Bank 1 Short Term = 7.031 %
Fuel Trim Bank 1 Long Term = 11.719 %
Fuel Trim Bank 2 Short Term = 7.031 %
Fuel Trim Bank 2 Long Term = 11.719 %
Engine RPM = 2,643 rpm
Speed (OBD) = 72.7 mph
Timing Advance = 23.5 °
Intake Air Temperature = 59 °F
Mass Air Flow Rate = 105.72 g/s
Throttle Position(Manifold) = 20 %
Air Status = 0 byte
End of report.

Cold Idle;


75 MPH Cruise;


Idle after 50 mile highway drive;


What should I try next?_a_
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Old 03-28-2014, 01:43 AM   #2
Jussblazn
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I had the same codes on my ride. I replaced the MAF with an aftermarket one costing around $60-80 bucks, then reset it with a code reader. It's been about 600 miles and the SES light has not come back on.
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Old 03-28-2014, 03:04 AM   #3
NumbaOneNewb
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If all your ccv hoses aren't broken, which I'm not sure how you can see all of them, then it could be the diaphragm inside the ccv got ripped
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Old 03-28-2014, 11:14 AM   #4
cvx5832
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And remember, lean codes could also be a fuel delivery issue. Is the fuel pump original?
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Old 03-28-2014, 11:21 AM   #5
TFT
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I did inspect the ccv hoses as much as possible but I didn't see any leaks on hoses or on the valve itself. I did see some oil on the top of the crankcase in the area of the ccv though. Would a failed ccv diaphragm cause the high fuel trims I'm seeing? Or would there need to be a broken cracked hose hose as well?
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Old 03-28-2014, 11:24 AM   #6
TFT
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Quote:
Originally Posted by cvx5832 View Post
And remember, lean codes could also be a fuel delivery issue. Is the fuel pump original?
Not sure about the age of the pump. I borrowed a pressure gauge from Autozone and will check the fuel pressure this weekend.
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Old 03-28-2014, 11:38 AM   #7
DaHammer
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After going to the trouble of removing the throttle body boots you should have just replaced them. They are cheap and the cracks can difficult to see. I just replaced them on my '03 for the 2nd time and I couldn't find any cracks but a smoke machine found them pretty quick.

Your percentages are pretty low and just beyond the threshold that sets the SES light, so if it is leaks that is causing it, they are likely small ones. If it were me, my next step would be to smoke test it.
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Old 03-28-2014, 11:43 AM   #8
DaHammer
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Quote:
Originally Posted by TFT View Post
Not sure about the age of the pump. I borrowed a pressure gauge from Autozone and will check the fuel pressure this weekend.
Also check it for leak down. You should be around 50 PSI, it shouldn't leak down more than 7 or 8 PSI in 20 minutes after shutting down the car.

You may want to check the volume also. It should be a little over a quart in 30 seconds.

How much did the car set you back, if you don't mind me asking?
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Old 03-28-2014, 12:21 PM   #9
mcopenha
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Yeah, these are difficult codes to get rid of. You've done the following, which are all possible contributors, so that's good:

-fuel pump
-checked DISA and replaced o-ring , it was still functional and no rattle
-removed upper and lower boot, both were pliable with no cracks reinstalled
-cleaned throttle body, wasn't very dirty
-inspected ICV, it was clean inside no carbon
-cleaned MAF

I wasn't able to get rid of the codes until I removed the intake and went through everything. I did this at the same time as replacing the CCV, which, at your mileage, you should address.

I'm not sure if they can contribute to lean codes, but I had a bunch of vacuum hoses that needed to be replaced -- both the SAP and exhaust flap systems. It's hard to address tiny leaks without taking the entire intake off. Replacing the throttle body gasket, ICV grommet, and intake gaskets didn't hurt either.

So, bottom line, I would start with the CCV.

Last edited by mcopenha; 03-28-2014 at 12:25 PM.
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Old 03-28-2014, 03:46 PM   #10
TFT
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Could a vacuum leak cause the two LTFT's to be so far apart? LTFT2 is always higher.
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Old 03-29-2014, 02:19 PM   #11
TFT
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Just tested fuel pressure, it was 50 psi. It dropped to 44 psi right when I shut down the engine but held there for 20 minutes. I don't think fuel delivery is the issue unless the injectors are clogged.
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Old 03-29-2014, 02:56 PM   #12
lszlszx
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Freeze frame shows same LTFT on both banks. The codes were set at 72 MPH.
I am thinking MAF sensor. Maybe you can borrow one from someone for testing?
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Old 04-01-2014, 12:00 PM   #13
Zardoz33
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Had both those codes recently, as well as a "low circuit input" error for the maf (sorry forgot what code it was) but thankfully it ended up being only my disa. Good luck.
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Old 04-01-2014, 12:18 PM   #14
Mario0617
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If your MAF has a lot of miles/years on it, it could have just failed. Mine did, and before it did, the only codes it threw were p0171 and p0174. Replaced it, drove across the city and back, the SES went out itself and they haven't been back.
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Old 04-01-2014, 07:47 PM   #15
TFT
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Replaced the MAF

UPDATE: I found a small hole in the CCV vent tube so I repaired it with tape and ordered another. Fuel trims did not change much after fixing the hole. I also ordered a new VDO MAF from BMA and installed it today. The MAF definitely made a difference on the fuel trim numbers. Prior to the new MAF the LTFT's were never lower than 10 and usually shifted between 11.7 and 14 at idle and at cruise. Now LTFT1 shifts between 0 and 6 and LTFT2 shifts between 3 and 9.

LTFT2 seems to be 3% higher than LTFT1 but not always. Could this be O2 sensors going bad? Also, the LTFT's are still not at the idea readings of(0+3/-3). The SES light is still on but I've only driven about 50 miles with new MAF.

Here are Torque screen shots

At 45 MPH after 50 miles driven


Idle after 50 miles driven
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Old 04-02-2014, 05:42 AM   #16
NumbaOneNewb
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I would erase check engine light instead of waiting for it to go off
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Old 04-02-2014, 01:04 PM   #17
05swtc
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Can someone explain

It appears that after changing the MAF, the Grams/Second numbers after a 50 mile run at idle are very close. I would think a failed MAF would have resulted in a more significant change in that number. According to BMW, the MAF numbers should be 15 - 20 Kg/H at idle. TFT, your numbers are both a little lower than that (3.8 G/S = 13.68 Kg/H and 3.6 G/S = 12.96 Kg/H) but still close. Those numbers are affected by things like A/C and Temp and BP.
I wouold be interested in seeing those numbers from a known working MAF on a 330. If you cant tell i am having a very similar problem to TFT and would love to hear more input.

I also just noticed the Load % was different..if the car is an automatic, could one one those screen shots have been at idle and the other in gear?

Not trying to threadjack TFT.

Last edited by 05swtc; 04-02-2014 at 01:08 PM.
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Old 04-02-2014, 01:29 PM   #18
TFT
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Quote:
Originally Posted by 05swtc View Post
It appears that after changing the MAF, the Grams/Second numbers after a 50 mile run at idle are very close. I would think a failed MAF would have resulted in a more significant change in that number. According to BMW, the MAF numbers should be 15 - 20 Kg/H at idle. TFT, your numbers are both a little lower than that (3.8 G/S = 13.68 Kg/H and 3.6 G/S = 12.96 Kg/H) but still close. Those numbers are affected by things like A/C and Temp and BP.
I wouold be interested in seeing those numbers from a known working MAF on a 330. If you cant tell i am having a very similar problem to TFT and would love to hear more input.

I also just noticed the Load % was different..if the car is an automatic, could one one those screen shots have been at idle and the other in gear?

Not trying to threadjack TFT.
The g/s are very close. The difference is only .2-.4 g/s, but that is a 5%-10% difference at idle. When I installed the new MAF and started the engine, the LTFT's started falling and the STFT's were -15, the existing MAF was definitely under reporting. Now I'm trying to figure out why the LTFT's are still above zero and differ by 3%.

All at idle screen shots were taken in park or neutral.
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Old 04-02-2014, 02:06 PM   #19
05swtc
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TFT, I hope you dont take this wrong but the full range of the MAF is ~0-100G/S.. So the difference installing a new MAF made was more like .05 to .1%. You have to consider the full range. I don't see enough delta to agree that the MAF was bad. I had LTFT numbers similar to yours and it was a very small vacuum leak at the "F" connector. you may have temporarily sealed that leak while installing the new MAF..Time will tell.
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Old 04-02-2014, 03:01 PM   #20
TFT
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Quote:
Originally Posted by 05swtc View Post
TFT, I hope you dont take this wrong but the full range of the MAF is ~0-100G/S.. So the difference installing a new MAF made was more like .05 to .1%. You have to consider the full range. I don't see enough delta to agree that the MAF was bad. I had LTFT numbers similar to yours and it was a very small vacuum leak at the "F" connector. you may have temporarily sealed that leak while installing the new MAF..Time will tell.
I appreciate your comments, no offence taken. But I don't see where you are getting .05-.1% - (.2/3.8 = 0.0526 x 100% = 5.26% at idle). I am sure the g/s difference is greater at higher flows but the percent difference should be similar. I think the only reliable point for comparing MAF readings is at idle with no accessories running.

The LTFT numbers after MAF replacement are less than half of what they were before. I drove to work with the bad MAF and LTFT readings were 11.7%-16%. A new MAF was delivered to my office and I swapped it in the parking lot with a 6mm nut driver. The LTFT readings were less than half on the drive home.

I have taken the intake apart several times looking for leaks. I even replaced some of the vac lines including the f-connector line to the fuel filter. I doubt that I was able to seal an undiscovered leak by chance while swapping out the MAF.
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