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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Sun, Apr-15-2018, 11:25:04 PM   #1
S54Kaleb
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Default Strange codes and even stranger issues

What's going on everyone? Havent posted here in a long time as most of my questions have been answered by lurking. However I'm having an issue that is driving me insane. I daily drive my M3 (158k) and have put it through a total of 3 winters in my possession, scandalous I know. It's never ran particularly bad but I have battled some intermittent lean codes when its below 20F but have always gone away once its warmer than that and it's always ran fine and idled rock solid.

This year things have changed. It's been a very rough winter as we all know and my car has faced the coldest temps it's ever seen I'm sure as I live in Illinois and the car is from Georgia. Progressively as the cold season has gone on its started to develop a major stumbling on accel past 50% throttle and progressively worse idle up until now it will die if I dont give a little gas until SAP turns off. When it warms up it idles fine but will occasionally hunt on idle even on a warm start. The codes I'm getting know are BMW code 174 and 175 on a Snap-On scanner which read in the scanner as Fuel System Diagnosis Bank 1 & 2. So I'm gathering it's not the same as the normal P0174 & P0175 codes.

I tried to test fuel pressures this weekend and was unable as our shop doesn't have the goofy M8 x .75 fuel test adapter. I know the pump is either original or at least 50k old since I've never changed it. I've smoke tested the intake and fixed a leak but the problem persists. I'm planning on changing the regulator and filter and have cleaned the MAF but I'm stumped. Anyone that can point me in the right direction as far as diagnosis would be met with a firm virtual high five. Sorry for the wall of text just wanted to give good background on situation.

Edit: Forgot to add that on warmer days the idling issue is almost non-existent and the acceleration issue is much less noticeable but still there.
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Last edited by S54Kaleb; Sun, Apr-15-2018 at 11:28:35 PM.
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Old Sun, Apr-15-2018, 11:51:48 PM   #2
ggrslc
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Default Re: Strange codes and even stranger issues

Quote:
Originally Posted by S54Kaleb View Post
What's going on everyone? Havent posted here in a long time as most of my questions have been answered by lurking. However I'm having an issue that is driving me insane. I daily drive my M3 (158k) and have put it through a total of 3 winters in my possession, scandalous I know. It's never ran particularly bad but I have battled some intermittent lean codes when its below 20F but have always gone away once its warmer than that and it's always ran fine and idled rock solid.

This year things have changed. It's been a very rough winter as we all know and my car has faced the coldest temps it's ever seen I'm sure as I live in Illinois and the car is from Georgia. Progressively as the cold season has gone on its started to develop a major stumbling on accel past 50% throttle and progressively worse idle up until now it will die if I dont give a little gas until SAP turns off. When it warms up it idles fine but will occasionally hunt on idle even on a warm start. The codes I'm getting know are BMW code 174 and 175 on a Snap-On scanner which read in the scanner as Fuel System Diagnosis Bank 1 & 2. So I'm gathering it's not the same as the normal P0174 & P0175 codes.

I tried to test fuel pressures this weekend and was unable as our shop doesn't have the goofy M8 x .75 fuel test adapter. I know the pump is either original or at least 50k old since I've never changed it. I've smoke tested the intake and fixed a leak but the problem persists. I'm planning on changing the regulator and filter and have cleaned the MAF but I'm stumped. Anyone that can point me in the right direction as far as diagnosis would be met with a firm virtual high five. Sorry for the wall of text just wanted to give good background on situation.

Edit: Forgot to add that on warmer days the idling issue is almost non-existent and the acceleration issue is much less noticeable but still there.


You’re on the right track. I think you will find you are running way too lean for a cold engine. Probably a little lean when warm as well but not lean enough to stumble or cook you valves.


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Old Mon, Apr-16-2018, 12:12:22 AM   #3
exodus454
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Default Re: Strange codes and even stranger issues

Front o2 sensors?
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Old Mon, Apr-16-2018, 12:36:01 AM   #4
S54Kaleb
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Default Re: Strange codes and even stranger issues

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Originally Posted by exodus454 View Post
Front o2 sensors?
Drove around parking lot of our shop and idled for a bit watching O2 data stream. All are in the realm of .8-.9v. B1S2 looked a little odd on the graph but its actual voltage readings were normal, granted this was on a warmer day where the issues are less noticeable. Planning on taking scanner this week and recording fuel trims on my way home.
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Old Mon, Apr-16-2018, 12:50:08 AM   #5
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Default Re: Strange codes and even stranger issues

.8-.9 is definitely at the outside of the range for a narrowband sensor. Depending on the scanner it may or may not show the sensor oscillating, but it should be. My guess is you either have a leak or a failing sensor that adaptations are masking, if you check your fuel trims they're probably adapted closely to the DTC threshold.
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Old Mon, Apr-16-2018, 06:47:14 AM   #6
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Default Re: Strange codes and even stranger issues

Front o2 sensors should be oscillating between around 0.1 and 0.8 and tell you how the car is running. Rear o2 sensors should be a lot more stationary around 0.7 as they just look at efficiency of the cats.

The fact that ALL(?) your sensors are showing 0.8 means fronts are either bad or you are just running super rich. O2 sensor simply measures amount of air in exhaust and is represented via a small amount of voltage. Low air content would be represented by a larger (closer to 0.8 volts) voltage number and means it's running rich. Larger air content would show up as lower (closer to 0.1 volts) and mean it's running lean.

What are your additive and multiplicative fuel trims (ltft)?

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Old Mon, Apr-16-2018, 12:25:03 PM   #7
S54Kaleb
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Default Re: Strange codes and even stranger issues

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Originally Posted by mrgizmo04 View Post
Front o2 sensors should be oscillating between around 0.1 and 0.8 and tell you how the car is running. Rear o2 sensors should be a lot more stationary around 0.7 as they just look at efficiency of the cats.

The fact that ALL(?) your sensors are showing 0.8 means fronts are either bad or you are just running super rich. O2 sensor simply measures amount of air in exhaust and is represented via a small amount of voltage. Low air content would be represented by a larger (closer to 0.8 volts) voltage number and means it's running rich. Larger air content would show up as lower (closer to 0.1 volts) and mean it's running lean.

What are your additive and multiplicative fuel trims (ltft)?

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I worded that incorrectly. The fronts are around .1 on the low end of the oscillation. The tears are very much the same, although the scope pattern looks very close to the before cat sensors. Will check fuel trims and report back.
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Old Fri, Jun-01-2018, 04:20:39 PM   #8
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Default Re: Strange codes and even stranger issues

Update to anyone having this problem. Went ahead and replaced Fuel Pump, Regulator and Filter and issue was resolved.
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Old Fri, Jun-01-2018, 04:42:59 PM   #9
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Default Re: Strange codes and even stranger issues

Nice! Inline with your o2 readings of fuel "starvation". Happy to see another one fixed.
Quote:
Originally Posted by S54Kaleb View Post
Update to anyone having this problem. Went ahead and replaced Fuel Pump, Regulator and Filter and issue was resolved.
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Discussing Strange codes and even stranger issues in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)