27aa Pre-Cat O2 sensor EML-Trouble Shooting Advice Needed - BMW M5 Forum and M6 Forums
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post #1 of 8 Old 11th February 2018, 04:34 PM Thread Starter
kei03174
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27aa Pre-Cat O2 sensor EML-Trouble Shooting Advice Needed

/Users/JCK/Downloads/IMG_2952.MOV
Hala to all fellas from m5board
I am new to the board, although I have read lots of threads, I have never actually posted in the forum before
Here is my story, I have 2007 m6 for 38k miles.
I have replaced everything, from rod-bearings, internal high-pressure vanos line, 4 solenoids, even pre cat O2 sensors, and MAFs for both banks for the error above. however, my car surges, and my butt keep saying the torque is not linear throughout the RPM.
Every cold start, I have emission light on with ISTA has a code for o2 sensor plausibility limit on bank 1.
I suspect the leak on intakes or exhaust, but there aren't any external leak observed.
No misfire or anything, but she still detects more air than she calculated from MAF sensor, only on bank 1.
Attached is the video clip I think is weird during my data logging last night.
actual position of idle actuator on bank 2 is almost a twice as that on bank 2.
Seems like idle actuator on bank 1 is adapted to a rich condition from its o2 sensor. what seems to me so far is its trying to open less flap for complementing the extra air coming in to equalize with bank 2, if you follow what I mean.
Please help me, I love my car, it is love and hate situation driving her around, want her stand straight again on her feet.
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post #2 of 8 Old 11th February 2018, 04:42 PM Thread Starter
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post #3 of 8 Old 11th February 2018, 05:53 PM Thread Starter
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Okay, since nobody has replied to the thread,
Does any of your car has different opening values for idle actuators of both banks.
I personally don't think this is normal, or I am too sensitive.
and I am orienting myself if this is the cause for EML...
Anybody?
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post #4 of 8 Old 11th February 2018, 07:26 PM
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I'd start with the obvious and pursue the leak route or at least put the old o2 sensor back on, sometimes you get them bad it happens.

The banks are pretty much separate through out. The DME will try to adjust the idle actuator based on load, rpm and short term trims for that bank. They shouldn't affect each other bank to bank in this engine.

Though if you suspect the actuator it's easy, though a pain to switch bank to bank.

Also as a side if you removed the plenum on bank 1, I'd check the most obvious too,the rear PCV line is connected and not broke, the plenum boots are on the throttle bodies, clamped, and not damaged, it's possible to kink one putting it on.

I'd also move mafs bank to bank as well and check the connections and clamps too.

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post #5 of 8 Old 11th February 2018, 10:16 PM Thread Starter
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Quote:
Originally Posted by Ferris View Post
I'd start with the obvious and pursue the leak route or at least put the old o2 sensor back on, sometimes you get them bad it happens.

The banks are pretty much separate through out. The DME will try to adjust the idle actuator based on load, rpm and short term trims for that bank. They shouldn't affect each other bank to bank in this engine.

Though if you suspect the actuator it's easy, though a pain to switch bank to bank.

Also as a side if you removed the plenum on bank 1, I'd check the most obvious too,the rear PCV line is connected and not broke, the plenum boots are on the throttle bodies, clamped, and not damaged, it's possible to kink one putting it on.

I'd also move mafs bank to bank as well and check the connections and clamps too.
Ferris, sir thanks for your reply
my long term fuel trim is over shooting.
even if I reset the adaptation, it keeps rising until it threw me the Emission Warning for now almost every start.
I know two banks are seperated, shouldn't throttle actuator, likewise idle actuator be synchronized the amount of air it takes in? Unless both banks have a different intake or exhaust set up, with all due respect sir, I don't know why actuators are opening at different angles to each other.
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post #6 of 8 Old 11th February 2018, 10:20 PM Thread Starter
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nevertheless, PCV and other hidden rubber hoses will I check and boots on throttle bodies to the plenum.
Thanks
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post #7 of 8 Old 11th February 2018, 10:54 PM
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No the DME will adjust fueling not the actuators position in order to meet lambda targets.
It will adjust the actuators based on MAF trying to hit a relative fill and idle speed target. Assuming it's not running in alpha n mode.

That in mind, I'd like to see your maf readings and I suggest swapping them bank to bank as well. IIRC it should detect a maf fault based on flow vs expect target and is fairly good at it, but it's worth a shot as it takes 5 minutes to swap them.

The more I think about it, I'd like to see the maf readings.

Also check the idle hose first..

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Last edited by Ferris; 11th February 2018 at 10:55 PM.
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post #8 of 8 Old 11th February 2018, 11:10 PM Thread Starter
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Quote:
Originally Posted by Ferris View Post
No the DME will adjust fueling not the actuators position in order to meet lambda targets.
It will adjust the actuators based on MAF trying to hit a relative fill and idle speed target. Assuming it's not running in alpha n mode.

That in mind, I'd like to see your maf readings and I suggest swapping them bank to bank as well. IIRC it should detect a maf fault based on flow vs expect target and is fairly good at it, but it's worth a shot as it takes 5 minutes to swap them.

The more I think about it, I'd like to see the maf readings.

Also check the idle hose first..
Okay, so are you saying I might have less filling required for bank 1 because of its MAF reading more than Bank 2, so bank 2 tries to open twice more to meet the air fillings of bank 1.
Wow, what a sentence there, I will see if there is difference in two banks.
IMO the MAF are recently changed a week ago, and I don't recollect any significant difference for MAF readings between two banks. But I will still check when rain stops here in NY
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