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Old 03-27-2012, 04:34 PM   #1
garmcqui
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2001 E46 330i - Running rich and O2 sensor readings...

Hi all,

Been having some problems with my car running too rich (or thinking it's running too rich). Not rich enough to throw a code or CEL, but when I hook INPA up to it I see this in the fuel trims:



Here's a video to show some of the INPA live data, inlcuding what the oxygen sensors are doing:



MAF sensor and both pre-cat oxygen sensors have been changed recently, using genuine items (Siemens MAF and Bosch O2 sensors).

Do the lambda/oxygen sensor voltage readings look ok to you?
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Old 03-27-2012, 07:57 PM   #2
iansanderson
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the readings look ok to me. doesn't look like the DME is having to compensate too much for the sensors although you should replace the post-cat sensors with the pre-cat because the post-cat sensors monitor the performance of the pre-cat sensors.

are you getting any fault codes in the DME?
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Cheat Sheet:

GT1/ISIS/MoDiC = Factory authorized diagnostic system used by BMW dealerships across the world.

NCS Expert = BMW Factory R&D programming tool available on the internet (not intended for the public and not available to the dealership network)

OEM = Genuine BMW part only available from a franchised BMW dealership.

DME = Engine Management Computer
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Old 03-27-2012, 08:26 PM   #3
jfoj
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First thing I would probably check is the fuel pressure regulator vacuum hose both under the hood and near the fuel filter to make sure things are in good shape.

Then consider a fuel filter is it usually has the fuel pressure regulator built in.
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

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

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

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

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Old 03-29-2012, 02:29 PM   #4
garmcqui
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Ok I will have a look, although wouldn't a bust vacuum line usually cause lean running?

I've been thinking about replacing the fuel filter for a while, might just go ahead and do it.

Will let you know.

One other weird thing, if I unplug the MAF and go for a drive the car isn't really down on performance much. The engine sounds a bit less refined at idle and isn't as smooth in acceleration, but it's definitely not noticably slower. Everywhere I read says that unplugging it should result in greatly reduced performance? It doesn't being on any warning lights either.

The MAF was new (genuine Siemens) a few weeks ago, but the old one did the same. Any ideas?
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Old 03-29-2012, 02:39 PM   #5
jfoj
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The fuel pressure vacuum line can be a double edge sword. If it is leaking enough to cause the fuel pressure to increase, the increased fuel pressure causes the mixture to get rich and it may mast the vacuum leak to some extent.

The good news it this is pretty easy to figure out visually.

But if you replace the fuel filter, you can easily inspect the vacuum hose under the car and replace it while you are there.

Good luck.
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

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

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

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

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

Lower hose fan switch O-ring - BMW #13621743299
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Old 03-29-2012, 03:30 PM   #6
garmcqui
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I see.

Ok well thanks, I'll definitely have a look.

Quote:
Originally Posted by iansanderson View Post
the readings look ok to me. doesn't look like the DME is having to compensate too much for the sensors although you should replace the post-cat sensors with the pre-cat because the post-cat sensors monitor the performance of the pre-cat sensors.

are you getting any fault codes in the DME?
The LTFT's are at -8% on both banks, which is apparently the maximum limit without generating a code. So the ECU is trying its best to lean out the mixture. Any other e46 I've checked these have been much closer to 0%.

I thought the post-cat sensors just monitored the performance of the cats, and didn't have anything to do with fuelling?

I did get an error code once a few weeks ago, but I cleared it and it never reappeared:


Last edited by garmcqui; 03-29-2012 at 03:37 PM.
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Old 10-11-2012, 06:44 PM   #7
YOnpds
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Good info. Thanks.
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Old 10-27-2012, 10:27 AM   #8
5eth
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garmcqui
i have same problem on my M54B22 (miltiplicative near -10% on both banks), were replaced throttle, MAF, 02 sensors, camshaft sensors (intake and exaust), fuel and air filters, fuel pressure is 3,4 bar, catalysts removed. Did you find any solution?

Last edited by 5eth; 10-27-2012 at 10:28 AM.
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