Bad AFR oscillation

5WAGN

Lurker
Jul 25, 2022
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Having a really bad oscillation while cruising, it has gotten progressively worse over the last few months since the car was initially tuned. Tuner has made several revisions but nothing is working. Anyone have any ideas on a possible cause or solutions?
 

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  • 2022-12-21 18_24_42 I8A0S 11-18 5wagn_TrakAssassin_MS_I8A0Sv_93_StkTrans_FRB_V8.1_WBAPT735.csv
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5WAGN

Lurker
Jul 25, 2022
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Having a really bad oscillation while cruising, it has gotten progressively worse over the last few months since the car was initially tuned. Tuner has made several revisions but nothing is working. Anyone have any ideas on a possible cause or solutions?
I’ve since changed both upstream 02 sensors and reset lambda adaptations but no success… anyone have any ideas?
 

carabuser

Lieutenant
Oct 2, 2019
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It's one of the many diagnostic routines for the O2 sensors. Could be either upstream or downstream.

Do you have any error codes active? Or any that would be active that are disabled in the tune?

You can see the AFR readings being manipulated so that the DME can measure the reponse.
1675436514928.png
 

PupkinRacing

Specialist
Aug 31, 2017
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Madison, Wisconsin
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Bmw 135i
It's one of the many diagnostic routines for the O2 sensors. Could be either upstream or downstream.

Do you have any error codes active? Or any that would be active that are disabled in the tune?

You can see the AFR readings being manipulated so that the DME can measure the reponse.
View attachment 77843
What’s the fix for this if I’m getting secondary o2 sensor codes. Sensors have been replaced.
 

PupkinRacing

Specialist
Aug 31, 2017
79
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Madison, Wisconsin
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Bmw 135i
What are the codes and what are your mods? Did you replace with genuine sensors?
335CCE66-9BE3-425B-A064-294C00077197.png

This is the code. But I feel it’s a little unrelated because the wiring on the connector is a little messed up. I can clear the code and the problem is still there. Code will stay off for a week or so sometimes. If I clear adaptations the oscillations stop for a couple weeks but always come back. Mods are 19t’s fbo, pr stage 3.5 lpfp, PFS pod, motive flex fuel kit tuned by v8bait. Normally I’d ask him but he has since stopped tuning.
 

carabuser

Lieutenant
Oct 2, 2019
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View attachment 77849
This is the code. But I feel it’s a little unrelated because the wiring on the connector is a little messed up. I can clear the code and the problem is still there. Code will stay off for a week or so sometimes. If I clear adaptations the oscillations stop for a couple weeks but always come back. Mods are 19t’s fbo, pr stage 3.5 lpfp, PFS pod, motive flex fuel kit tuned by v8bait. Normally I’d ask him but he has since stopped tuning.
That's an error code on bank 1 rear O2. The DME is getting an unexpected reading when the fuel is cutoff in overrun. Most likely still seeing a reading that indicates fuel is being injected. So usually means an injector is leaking or the sensor is bad. In your case I would just fix that wiring.
 

PupkinRacing

Specialist
Aug 31, 2017
79
21
0
Madison, Wisconsin
Ride
Bmw 135i
That's an error code on bank 1 rear O2. The DME is getting an unexpected reading when the fuel is cutoff in overrun. Most likely still seeing a reading that indicates fuel is being injected. So usually means an injector is leaking or the sensor is bad. In your case I would just fix that wiring.
Thanks for the tips. Going to try and find a harness I can get off a parts car or something to fix the wiring. Or maybe have to hardwire my o2 sensor because the tube/tunnel that the 02 sensor plugs into is what is messed up. Although it’s very possible I have a leaking injector too. Index 12s but they are like 3-4 years old now.
 

5WAGN

Lurker
Jul 25, 2022
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Ask your tuner what error codes he disables in the tune. Behaviour like that is usually caused by a diagnostic failure, just because the code is disabled doesn't mean the diagnostics are.
Ok, been working with the tuner trying to find the issue so I know he’s looking at all parameters but I’ll ask. Do you think I should jus go ahead and replace the downstream sensors too? Also, unrelated question- does the E60-61 have secondary cats? Spent some time under the car recently and it looks like there are two more cats before the resonator…
 

carabuser

Lieutenant
Oct 2, 2019
870
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Ok, been working with the tuner trying to find the issue so I know he’s looking at all parameters but I’ll ask. Do you think I should jus go ahead and replace the downstream sensors too? Also, unrelated question- does the E60-61 have secondary cats? Spent some time under the car recently and it looks like there are two more cats before the resonator…
I doubt he'll be able to do anything meaningful as he's probably working just with what's in the public XDF.

If he hasn't disabled any codes relating to the O2 sensors then I can give you a couple of extra channels to log that might pick up what diagnostic is causing the issue. The most likely cause is bad secondaries though.

I think all N54 cars have secondary cats. They aren't monitored at all so won't be a problem.
 

5WAGN

Lurker
Jul 25, 2022
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I doubt he'll be able to do anything meaningful as he's probably working just with what's in the public XDF.

If he hasn't disabled any codes relating to the O2 sensors then I can give you a couple of extra channels to log that might pick up what diagnostic is causing the issue. The most likely cause is bad secondaries though.

I think all N54 cars have secondary cats. They aren't monitored at all so won't be a problem.
Ok, shot him a text to ask about the codes. Yeah any addtl. log channel recommendations you’ve got would be greatly appreciated.
 

5WAGN

Lurker
Jul 25, 2022
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0
I doubt he'll be able to do anything meaningful as he's probably working just with what's in the public XDF.

If he hasn't disabled any codes relating to the O2 sensors then I can give you a couple of extra channels to log that might pick up what diagnostic is causing the issue. The most likely cause is bad secondaries though.

I think all N54 cars have secondary cats. They aren't monitored at all so won't be a problem.
What channels would you recommend monitoring?
 

carabuser

Lieutenant
Oct 2, 2019
870
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766
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Z4 35i & 335i
They would be custom ones but finding the activation flags for O2 diagnostic in I8A0S is too much hassle.

Have you tested to see if this happens on a stock tune?
 

digitalashley

Specialist
Apr 8, 2019
78
25
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135i n54, E87 N54
Hey any updates to this? I've had this issues for sometime . One car I own has it worse the other more recently and is much less noticeable. Such an annoying thing loading the tune again via MHD stops the issue for a period but always comes back.