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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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  #1  
Old 06-18-2017, 09:57 AM
Bimmertastic Bimmertastic is offline
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P0174, p0171, cel

Hello there,

I've been trying to track this problem down for like a year now. Recently had a new CCV installed, then got codes P0492 and P0491, turned out to be a missing vacuum hose behind the intake manifold.

Once I plugged that hose in, CEL and P0171 and P0174, rough idle, loss of power, car is jerky at acceleration and downshifts hard. City Mpg is around 7, but highway is an impeccable mid 20'. All my boots are good, there is a slight suction at the oil cap, sometimes the car smells like gas outside around the front of the car. If I unplug my MAF, the normal Exclamation point dash light comes on, the car shifts really hard/weird, bad mpg too. I'm going to check my fuel pressure soon, but theres got to be a vacuum leak somewhere.

Also, theres this sound I found, made this video. I was having a friend press the gas slightly so I could hear it better:


What I've fixed so far:
Fuel filter
CCV
VCG
DISA (1.5 years ago, but works fine)
replaced all vacuum hoses
spark plugs
Intake manifold gasket
MAF - I cleaned it and it made my MPG go from 11mpg to 16mpg when I first cleaned it (yay), but seems to work fine still.
a few more things (can't remember right now)

I've had these codes come and go for about a year now, but now my OBDII scanner is telling me it might not pass emissions this year, so something is obviously getting worse.

My Fuel Trim:

STFT1: sometimes it's REALLY negative or REALLY positive (-11% to 11%)
STFT2: same as STFT1

LTFT1: Always around 10-ish%
LTFT2: same as LTFT1

-----------------------------------
Short Term Fuel Trim Bank 1: -11.7%
Short Term Fuel Trim Bank 2: -8.6%
Long Term Fuel Trim Bank 1: 10.2%
Long Term Fuel Trim Bank 2: 10.9%
------------------------------------
O2 Senors:
Sometimes System B will be open loop when it needs to be, but System A is always closed loop.

Sorry if this seems really long, I'm just trying to give the most information I can, I feel like I've checked everything, but apparently not. Any help would be great, thanks!

Last edited by Bimmertastic; 06-18-2017 at 10:08 AM.
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  #2  
Old 06-18-2017, 10:04 AM
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Fast Bob Fast Bob is offline
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O2 sensors typically need replacing @ around 120,000 miles. Replacing the VANOS seals wouldn`t be a bad idea either.
Good luck !
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  #3  
Old 06-18-2017, 10:06 AM
Bimmertastic Bimmertastic is offline
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Quote:
Originally Posted by Fast Bob View Post
O2 sensors typically need replacing @ around 120,000 miles. Replacing the VANOS seals wouldn`t be a bad idea either.
Good luck !
Hey thanks for responding so quickly! That's what I was thinking too, but I wasn't completely sure. I'll give that a shot.

Also, I just posted a video (if you refreshed the page) of a sound I can't diagnose. It makes that vacuum/blowing sound, then the car accelerates.
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  #4  
Old 06-18-2017, 10:08 AM
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All2kool All2kool is offline
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I chased a P0171/0174 for a few months myself. I've not seen either code since replacing my original Fuel Pump that had provided 135k miles of service.
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  #5  
Old 06-18-2017, 10:10 AM
Bimmertastic Bimmertastic is offline
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Originally Posted by All2kool View Post
I chased a P0171/0174 for a few months myself. I've not seen either code since replacing my original Fuel Pump that had provided 135k miles of service.
Alrighty, I'll definitely give this a shot with some new 02 Sensors, thanks! . I'm going to test my fuel pressure soon anyways, so that will give me a better idea. I'm the 6th owner of this car and I looked at the fuel pump and it looks like it was replaced soon before I bought the car, but hey, you never know lol.
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  #6  
Old 06-18-2017, 10:52 AM
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Fast Bob Fast Bob is offline
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Quote:
Originally Posted by Bimmertastic View Post
Alrighty, I'll definitely give this a shot with some new 02 Sensors, thanks! . I'm going to test my fuel pressure soon anyways, so that will give me a better idea. I'm the 6th owner of this car and I looked at the fuel pump and it looks like it was replaced soon before I bought the car, but hey, you never know lol.
If that pump actually IS a replacement, there`s always the possibility that it`s an el cheapo unit, and not up to the job....
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  #7  
Old 06-18-2017, 10:59 AM
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All2kool All2kool is offline
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Quote:
Originally Posted by Bimmertastic View Post
...and I looked at the fuel pump and it looks like it was replaced soon before I bought the car, but hey, you never know.
I know mine was original to the car as the top of it was filthy dirty and it still utilized the 'use once only clamp' on the fuel out line. Cut it off with wire cutters I did.

That sound? Sounds like a vacuum leak to me. Maybe the diaphragm on the DISA is toast. You can remove the DISA and test that theory.

Last edited by All2kool; 06-18-2017 at 11:02 AM.
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  #8  
Old 06-18-2017, 06:08 PM
Bimmertastic Bimmertastic is offline
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Quote:
Originally Posted by All2kool View Post
I know mine was original to the car as the top of it was filthy dirty and it still utilized the 'use once only clamp' on the fuel out line. Cut it off with wire cutters I did.

That sound? Sounds like a vacuum leak to me. Maybe the diaphragm on the DISA is toast. You can remove the DISA and test that theory.
Yeah, well I had taken my seat out for extra room and stuff for other reasons, but the fuel tank seal ring looked brand new and shiny black (never seen that before). I think I'll replace it anyways, I've heard they go out a lot in E46s. Ok, thank you for that tip .

Yeah, I can't figure out where it's coming from. It sounds like its coming from the DISA or somewhere around there. I had the DISA replaced with a Chinese rebuilt one, so maybe the seal is toast on it? I can just buy an o-ring and pop it on rather than buying a whole new unit, right? I had taken the DISA out a few months ago and it held a strong vacuum with my finger.

Also, I had sprayed some starting fluid around the DISA seal and it didn't seem to make much difference.
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  #9  
Old 06-18-2017, 06:10 PM
Bimmertastic Bimmertastic is offline
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Originally Posted by Fast Bob View Post
If that pump actually IS a replacement, there`s always the possibility that it`s an el cheapo unit, and not up to the job....
I have a feeling that it might just be that, the seal ring (on the outside that screws together) looks shiny black/perfect condition, which startled me because I though they looked different. I'll probably replace just incase, I heard they go out easily in E46s.
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  #10  
Old 06-18-2017, 08:21 PM
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All2kool All2kool is offline
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Originally Posted by Bimmertastic View Post
I can just buy an o-ring and pop it on rather than buying a whole new unit, right?
Yes. I replaced my factory 'seal' with a Fluorosilicone O-Ring. I also put a bead of Gorilla Silicone Sealer around the outside ring of the Diaphragm, just for good measure.

Last edited by All2kool; 06-18-2017 at 08:22 PM.
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  #11  
Old 06-18-2017, 08:25 PM
Bimmertastic Bimmertastic is offline
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Originally Posted by All2kool View Post
Yes. I replaced my factory 'seal' with a Fluorosilicone O-Ring. I also put a bead of Gorilla Silicone Sealer around the outside ring of the Diaphragm, just for good measure.
Oh ok, perfect. I just picked up an O-Ring for my DISA at BavAuto.com. Hopefully this helps. Thank you for your help too .
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  #12  
Old 06-26-2017, 04:37 PM
Bimmertastic Bimmertastic is offline
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Originally Posted by Fast Bob View Post
If that pump actually IS a replacement, there`s always the possibility that it`s an el cheapo unit, and not up to the job....
Never mind when I said I thought it was a replacement pump, I opened the back cap hiding the fuel pump and there were helicopters (little seeds) all over, the metal seal was all rusty and it still has the OEM Genuine BMW clamp on the fuel hose haha. Replacing all soon.

I did just swap the O-Ring on my DISA to see if that did anything, it didn't by the way.

I tested my fuel pressure and got 40PSI with key out and car off, 42PSI with key on and car off, and 45 PSI with car running at idle. I'm not sure if that's off, but I think its a little low.

Replacing O2 Sensors once I find a socket for it, probably in a few days .

Thanks again for help guys.


BTW, I'm at 139,880 Miles. It's a 2003 330xi
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  #13  
Old 06-29-2017, 01:38 PM
Bimmertastic Bimmertastic is offline
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Mein Auto: 2003 330xi 141,060 Miles
Quote:
Originally Posted by All2kool View Post
Yes. I replaced my factory 'seal' with a Fluorosilicone O-Ring. I also put a bead of Gorilla Silicone Sealer around the outside ring of the Diaphragm, just for good measure.
Hello again, about 5 days ago I installed the new O-Ring on my DISA and it made a world of a difference. It feels like I've gained 50hp, its insane. So, that fixed P0171 oddly enough, but now I'm stuck with P0174.
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  #14  
Old 06-29-2017, 01:42 PM
Bimmertastic Bimmertastic is offline
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Mein Auto: 2003 330xi 141,060 Miles
Quote:
Originally Posted by All2kool View Post
I know mine was original to the car as the top of it was filthy dirty and it still utilized the 'use once only clamp' on the fuel out line. Cut it off with wire cutters I did.

That sound? Sounds like a vacuum leak to me. Maybe the diaphragm on the DISA is toast. You can remove the DISA and test that theory.
Yeah, the DISA fixed a lot of my problems, but not all. I'm going to do my Fuel Pump very soon too, had to wait for BavAuto.com to get the fuel tank seal in stock. I had the code P0174 about 2-3 months ago and a fuel filter solved it for that time, so I'm assuming its a fuel issue I'm having. Hopefully the fuel pump solves it . Also, I do have an original fuel pump, before I had just looked at the cover that is just under the seat, not the actual pump. I'll be back on this post in a few days and update you guys.
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  #15  
Old 07-04-2017, 07:55 PM
Bimmertastic Bimmertastic is offline
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Mein Auto: 2003 330xi 141,060 Miles
Quote:
Originally Posted by Fast Bob View Post
O2 sensors typically need replacing @ around 120,000 miles. Replacing the VANOS seals wouldn`t be a bad idea either.
Good luck !
Hey there again Fast Bob, I finally replaced my O2 Sensors and while they did make a noticeable different in my performance and idle, I still have that code.

Edit: I forgot to mention that I just recently noticed my MAF was reading 0.54 lb/min or 3.08 g/s... that's pretty low, isn't it?

Last edited by Bimmertastic; 07-04-2017 at 08:22 PM.
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