Datalog E92 335i Cylinder One Misfire & Lambda AFR, Help!

[ClaytonT]

Hi Guys!

I’m new to the forums and a first time poster. Im hoping to get a bit of advice on a problem I’ve ran into as beside trawling YouTube tutorials and scrolling on forums I’m fairly inexperienced with the tuning of these vehicles.

Essentially I have had a 29CD code (Cylinder 1 combustion misfire) start popping up over the last few days. Spark plugs were replaced less than 5000km ago and coils checked at the same time. I had the same issue when I first purchased the car (it was and still is, running a third party stage one tune) and changing the spark plugs fixed it so am I right in assuming that now a coil has gone bad? Or do you guys recommend I go to one step colder plugs?

I’ve attached the log of the pull which caused the misfire, hopefully I’ve got the BBCode right lol. Is there any chance someone could take a look at the log and let me know their thoughts? I’m also curious about the Lambda AFR numbers and why it seems to have gone off the charts.

Thank you very much !
Clayton

Misfire Log

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[RuskiRacer]

Your pulling like 3 degrees of timing in cylinder 1. And your afrs are way off from each other. What mods are done to the car? What fuel?

 

[ClaytonT]

Your pulling like 3 degrees of timing in cylinder 1. And your afrs are way off from each other. What mods are done to the car? What fuel?

yeah it’s not good, it’s on 98 octane and is FBO with VRSF Catless Downpipes, VRSF 7.5inch FMIC, VRSF Intakes and Aluminium Chargepipe, Factory Oil Cooler

 

[RuskiRacer]

Have you tried resetting 02 sensor adaptations? If that doesn't do anything you may just want to get new 02 sensors. And 1 step or 2 step colder plugs won't hurt either. You can fry the 02 sensors by doing to many pulls on them when they lean out like that

 

[RuskiRacer]

You have good fuel pressure, but by the end of the pull you can start to see the afrs really start to very from each other. What index injectors are on the car?

 

[ClaytonT]

You have good fuel pressure, but by the end of the pull you can start to see the afrs really start to very from each other. What index injectors are on the car?
View attachment 48600

Interesting! I assume the injectors are stock, there’s no details on them in the mod list I got from the previous owner (I’ve only owned the car for four months). Could you please tell me how to reset the 02 adaptations? Is it through MHD?

 

[RuskiRacer]

Yes you can reset them through mhd. Bmw had 12 revisions of injectors for the n54. Some of them were more problems than others and there really prone to carbon buildup. How many miles on the car?

 

[ClaytonT]

Yes you can reset them through mhd. Bmw had 12 revisions of injectors for the n54. Some of them were more problems than others and there really prone to carbon buildup. How many miles on the car?

Ah interesting, I’ll pull the cover off and have a look to see which index they are. It is an ‘07 so as early as it gets for the e92 I suppose, car has 90,000 miles on it

 

[RuskiRacer]

Putting a catch can on the car if it doesn't have one already would be a good idea as well. I'd reset adaptations and go from there. 02 sensors aren't to expensive which is most likely the case since your short term fuel trims look ok. You could let the car sit over night and pull the plugs tommorow and smell if there's any fuel on them. If the coilpacks are original you may want to get some fresh ones. Delphi or eldors are usually my go to. You can get them on fcp euro with there lifetime warranty.

 

[ClaytonT]

Putting a catch can on the car if it doesn't have one already would be a good idea as well. I'd reset adaptations and go from there. 02 sensors aren't to expensive which is most likely the case since your short term fuel trims look ok. You could let the car sit over night and pull the plugs tommorow and smell if there's any fuel on them. If the coilpacks are original you may want to get some fresh ones. Delphi or eldors are usually my go to. You can get them on fcp euro with there lifetime warranty.

Thanks man, it does actually have a catch can I forgot to mention that since it was installed on the car years ago. Alright cool I’ll give that a try. Probably a good idea to grab coil packs since I really should’ve done em with the plugs but thank you very much! I’ll give an update when I get some more info

 

[JohnDaviz]

You should log Fuel Mod and probably RPM..

Your STFTs are flatlining. Thus your absurdly high AFRs.

 

[ClaytonT]

You should log Fuel Mod and probably RPM..

Your STFTs are flatlining. Thus your absurdly high AFRs.

Alright thanks I will. Had a thought, if a bad coil is indeed causing a misfire on cyl 1, could the dme be detecting this and cutting fuel to that cylinder thus leaning the bank one mixture out and flatlining the STFT?

 

[JohnDaviz]

yes. If Misfire detected, STFTs for both banks flatline. At least it was the same on my car.

 

[ClaytonT]

yes. If Misfire detected, STFTs for both banks flatline. At least it was the same on my car.

Interesting, definitely gonna switch these coils around tomorrow and fingers crossed that solves it - if I add any more logs I’ll make sure to monitor RPM and Fuel Mode. Would you mind telling me what Fuel Mode monitors/means

 

[JohnDaviz]

Logging the Fuel Mode should just confirm that the car is going into limp mode during the event that causes the STFT flatlining.

So most probably Fuel Mode 15 should show in the log

 

[ClaytonT]

Logging the Fuel Mode should just confirm that the car is going into limp mode during the event that causes the STFT flatlining.

So most probably Fuel Mode 15 should show in the log

View attachment 48605

awesome. appreciate it, I’ll make sure to have that up next time

 

[dpaul]

Just a suggestion - your logging technique is not optimal - you dribble the throttle on then dribble it off, which confounds interpretation of many parameters including AFRs

1) Add RPM as a log parameter
2) At about 2500rpm in 3rd got to WOT and HOLD IT FULLY OPEN until above 6K rpm, preferably 6500.
3) Shift into 4th and hold it WOT for another few seconds. If you can't find a speed-tolerant place to do this, at least do it 2nd to 3rd gear.
But keep the throttle wide open or fully closed

Also you are triggering torque limiter 1 so make sure you fully disable DSC/traction control (long press of button) before you log.

That said it is clear that Bank 1 STFT is maxing i.e. adding as much fuel trim as possible and even so the AFR appears lean. Your bank 2 STFT and AFR are actually OK, not ideal but OK. This is consistent with a clogged injector in bank 1, which is the simplest explanation (though not necessarily the correct one) for your issue.

Finally, when you say "AFR off the charts" if you mean the fact that they read 234 after throttle closure, that is normal. If they didn't quickly return to 234 that would indicate a leaky injector or a dying pre-cat O2 sensor. If you meant the abnormal bank 1 AFR which reaches as high as 30 when you still have 70% throttle, then never mind.

 

[doublespaces]

Not bad for a first time poster, understands how to embed a graph as well.

 

[dpaul]

True that. Also, I apologize for not noticing the thread was 6 months old and that further discussion would likely be moot

 

[doublespaces]

I moved it to the troubleshooting section, so it can still hold usefulness to future google searchers and won't bother anyone in the main N54 section.