[ozymandias435]

Hey guys/girls,

Just changed the ignition coils on 2015 435 GC. Running FBO + BM3 Stg 2 + NGK gapped to .022.

I changed the plugs a few weeks back but did not use new coils. I decided that I should get new coils cause the car is at 70k miles so I did and just finished installing them. Went with the Ignition Projects N55 set. Cranked right up, idled beautifully, but then I got a P0171 System Too Lean Bank 1. Everything is plugged in and connected and the only change is the brand new coils. Have never had this code before. I also turned off the cold start setting yesterday morning on BM3 so do not know if that is relevant in any way? Those are the only two things different as of recent. Anyone else experience this after changing coils? When I did crank the car I had the hood open and engine cover off while I made sure the car was tip top and the car smelled very gassy around the engine bay.

Thank you for any input or help!

[bdragon46]

Sounds like the fuel is not get burnt which means no spark. Have tried the old coils? Double check that the new coils are all properly connected to the plugs. Also try swapping the coils around to see if the code moves to a different bank

[thejeremyman9]

I think this is another lesson of don't fix it if it's not broken, lol.

Did the code appear at idle or after driving? Did you try clearing the code and doing a little driving to see if it came back?

Any datalogs of the issue? We need to see actal vs target AFR.

[ozymandias435]

Originally Posted by thejeremyman9

I think this is another lesson of don't fix it if it's not broken, lol.

Did the code appear at idle or after driving? Did you try clearing the code and doing a little driving to see if it came back?

Any datalogs of the issue? We need to see actal vs target AFR.

Code appeared at idle. I cleared it and drove around a bit and it hasnt come back. Car idled and actually ran better with the new coils. Cleaner and smoother. Also checked all the coils again and made sure they were snug with all connections tight. I was reading an article that mentioned STFT and LTFT so I checked both of those with the live data. The STFT was idling around 0 and the LTFT was idling between 9-11% and upon throttle would drop down to around 0.

Will attempt to get a log tonight

[thejeremyman9]

Originally Posted by ozymandias435

Code appeared at idle. I cleared it and drove around a bit and it hasnt come back. Car idled and actually ran better with the new coils. Cleaner and smoother. Also checked all the coils again and made sure they were snug with all connections tight. I was reading an article that mentioned STFT and LTFT so I checked both of those with the live data. The STFT was idling around 0 and the LTFT was idling between 9-11% and upon throttle would drop down to around 0.

Will attempt to get a log tonight

I wouldn't stress about it if it hasnt come back... but just keep an eye out for codes/shadow codes. Its possible the car just needed time to adapt to the new coils.

STFT is the main one to keep an eye on. Around 0 is good; it means the DME isnt really making major corrections based on AFR. You can always monitor lambda versus target. If you see spikes in AFR (higher = leaner), you might have a misfire or other issue.

[ozymandias435]

Originally Posted by thejeremyman9

I wouldn't stress about it if it hasnt come back... but just keep an eye out for codes/shadow codes. Its possible the car just needed time to adapt to the new coils.

STFT is the main one to keep an eye on. Around 0 is good; it means the DME isnt really making major corrections based on AFR. You can always monitor lambda versus target. If you see spikes in AFR (higher = leaner), you might have a misfire or other issue.

It makes sense that the engine may have needed a bit of time to adapt. I will keep an eye on it. Thank you for responding. You've helped me a few times before!

[Fudz]

Originally Posted by bdragon46

Sounds like the fuel is not get burnt which means no spark. Have tried the old coils? Double check that the new coils are all properly connected to the plugs. Also try swapping the coils around to see if the code moves to a different bank

unburnt fuel means rich


a different bank means a Vee engine

[thejeremyman9]

Originally Posted by Fudz

unburnt fuel means rich


a different bank means a Vee engine

Sorry, but this is wrong. Unburnt fuel means LEAN. O2 sensors read oxygen, not fuel. If you have a misfire or other issue that causes the mixture to not be combusted, you get excess O2 in exhaust, which reads LEAN.

[ozymandias435]

Originally Posted by thejeremyman9

I think this is another lesson of don't fix it if it's not broken, lol.

Did the code appear at idle or after driving? Did you try clearing the code and doing a little driving to see if it came back?

Any datalogs of the issue? We need to see actal vs target AFR.

Just took a log. Forgot to put the laptop in offline mode.....did the log.....studied it and then when i went back to look at it is was nowhere to be found. Is there a way to recover after the fact??

Either way I did find some interesting stuff on there.

-Ign 2 seems to be lower than the other 5 (3 points or so) for most of the rpms until the higher RPMs where it catches up
- Overboost around 3200 rpms (17.7/16.8)
- Load Actual is wayyyyyy low of Load Target. Not sure if they are supposed to match or not.

Went back and just did another log and made sure this one recorded. https://www.bootmod3.net/log?id=5ec2...729b5be725232a

This one is more of the exact same.

That ignition 2 problem is not on any of my other logs and the only difference is the new Ignition Coils.

Please take a look and see what you think about the numbers. You seem to be incredibly knowledgable with all of this.

Thanks man

[thejeremyman9]

Originally Posted by ozymandias435

Just took a log. Forgot to put the laptop in offline mode.....did the log.....studied it and then when i went back to look at it is was nowhere to be found. Is there a way to recover after the fact??

Either way I did find some interesting stuff on there.

-Ign 2 seems to be lower than the other 5 (3 points or so) for most of the rpms until the higher RPMs where it catches up
- Overboost around 3200 rpms (17.7/16.8)
- Load Actual is wayyyyyy low of Load Target. Not sure if they are supposed to match or not.

Went back and just did another log and made sure this one recorded. https://www.bootmod3.net/log?id=5ec2...729b5be725232a

This one is more of the exact same.

That ignition 2 problem is not on any of my other logs and the only difference is the new Ignition Coils.

Please take a look and see what you think about the numbers. You seem to be incredibly knowledgable with all of this.

Thanks man

So no codes still right? Does the car "feel" like its running OK?

Not sure about recovering the log, i use MHD not BM3.

- For cyl 2, its not unusual to see some deviation in timing between cylinders. Now if it seems like cyl 2 is always and repeatably having issues, it might be worth investigating further. For example you could try swapping cyl 2 coil with another one and see if it follows the coil. You could also pull that plug and double check the gap. But the small deviations in the log aren't necessarily cause for concern.
- The overboost early is typical of BM3. I saw someone else overboosting 5psi... which is a bit much. Yours looks "fine" in that sense that its typical BM3 tune behavior.
- Also a artifact of BM3. They dont used a load based tune like stock or MHD, so your load will never be close to target. So not indicative of a problem.

[ozymandias435]

Originally Posted by thejeremyman9

So no codes still right? Does the car "feel" like its running OK?

Not sure about recovering the log, i use MHD not BM3.

- For cyl 2, its not unusual to see some deviation in timing between cylinders. Now if it seems like cyl 2 is always and repeatably having issues, it might be worth investigating further. For example you could try swapping cyl 2 coil with another one and see if it follows the coil. You could also pull that plug and double check the gap. But the small deviations in the log aren't necessarily cause for concern.
- The overboost early is typical of BM3. I saw someone else overboosting 5psi... which is a bit much. Yours looks "fine" in that sense that its typical BM3 tune behavior.
- Also a artifact of BM3. They dont used a load based tune like stock or MHD, so your load will never be close to target. So not indicative of a problem.

Still no codes. Car feels pretty solid. I wouldnt say it is running best it ever has under WOT. Does seem a fraction off.

Seems to be cyl 2. Ran 3 Logs today, lost 2 of them, but in all 3 logs Cyl 2 was laggy. Will let the engine bay cool down and I will pull that plug, check it, and swap coils 1 and 2.

Hard for me to think there is a coincidence with the CEL I got the other day about being lean right after changing the coils, smelling all of the gas, and now cyl 2 seems to be acting a fool.

what would you say the benefits are of load based tuning vs Bm3?

[thejeremyman9]

Originally Posted by ozymandias435

Still no codes. Car feels pretty solid. I wouldnt say it is running best it ever has under WOT. Does seem a fraction off.

Seems to be cyl 2. Ran 3 Logs today, lost 2 of them, but in all 3 logs Cyl 2 was laggy. Will let the engine bay cool down and I will pull that plug, check it, and swap coils 1 and 2.

Hard for me to think there is a coincidence with the CEL I got the other day about being lean right after changing the coils, smelling all of the gas, and now cyl 2 seems to be acting a fool.

what would you say the benefits are of load based tuning vs Bm3?

I would note your MAF reading also looks a little unstable... for some reason I have been seeing that with several people recently. Not sure what that is. Stock intake?

I am not entirely sure how much adaptations play into coils... i know there are specific flash options for different coils, so my initial thought was that there is some sort of DME adaptation going on, which could explain why you got a code right after install but it has not reappeared since. I suppose a misfire on cylinder 2 could also lead to a lean condition, but if there was a serious problem with that cylinder (coil/plug, etc) i think it would be more apparent.

I personally like the load based approach because i feel like it better adjusts for variations in atmospheric conditions to deliver consistent power and it is a bit more conservative in terms of implementing protective measures, e.g. throttle closures for overboost. Not going to say one is "better" than the other since they can both work, just my 2c. Load based is also OEM design.

[ozymandias435]

Originally Posted by thejeremyman9

I would note your MAF reading also looks a little unstable... for some reason I have been seeing that with several people recently. Not sure what that is. Stock intake?

I am not entirely sure how much adaptations play into coils... i know there are specific flash options for different coils, so my initial thought was that there is some sort of DME adaptation going on, which could explain why you got a code right after install but it has not reappeared since. I suppose a misfire on cylinder 2 could also lead to a lean condition, but if there was a serious problem with that cylinder (coil/plug, etc) i think it would be more apparent.

I personally like the load based approach because i feel like it better adjusts for variations in atmospheric conditions to deliver consistent power and it is a bit more conservative in terms of implementing protective measures, e.g. throttle closures for overboost. Not going to say one is "better" than the other since they can both work, just my 2c. Load based is also OEM design.

Thank you for the insight and for clarifying. I have been happy with BM3 so far. I will be going custom tune here in the coming months for sure.


What do you mean exactly by the MAF? what would stability or ideal MAF look like? I have Dinan CF Intake and aluminum pure inlet pipe. The silicon connection binding the two is difficult to get lock tight on the inlet pipe cause the inlet mouth is almost too close to the Dinan mouth if that makes sense. Could potentially be a small leak there. Will check that as well when I pop the hood

[thejeremyman9]

Originally Posted by ozymandias435

Thank you for the insight and for clarifying. I have been happy with BM3 so far. I will be going custom tune here in the coming months for sure.


What do you mean exactly by the MAF? what would stability or ideal MAF look like? I have Dinan CF Intake and aluminum pure inlet pipe. The silicon connection binding the two is difficult to get lock tight on the inlet pipe cause the inlet mouth is almost too close to the Dinan mouth if that makes sense. Could potentially be a small leak there. Will check that as well when I pop the hood

Look at the MAF readings in your log. It jumps up and down and isnt a smooth, continuously increasing curve. It doesn't really make sense for MAF readings to decrease up and down while RPM is constantly increasing (unless there is a lot of air turbulence at the MAF or potentially an issue). Also, check out this thread... hes on PS2 and chasing issues but interestingly enough he also has the dinan intake and his MAF readings showed the same behavior.... Apparently (near end of thread), the tuner he went to thought the MAF was the issue. https://f30.bimmerpost.com/forums/sh....php?t=1719860

As a point of comparison, here is a log of mine - check out the MAF curve; much smoother without those "oscillations." I am on stock intake with a drop in filter.
https://datazap.me/u/thejeremyman9/4...0&data=4-19-25

[ozymandias435]

Originally Posted by thejeremyman9

Look at the MAF readings in your log. It jumps up and down and isnt a smooth, continuously increasing curve. It doesn't really make sense for MAF readings to decrease up and down while RPM is constantly increasing (unless there is a lot of air turbulence at the MAF or potentially an issue). Also, check out this thread... hes on PS2 and chasing issues but interestingly enough he also has the dinan intake and his MAF readings showed the same behavior.... Apparently (near end of thread), the tuner he went to thought the MAF was the issue. https://f30.bimmerpost.com/forums/sh....php?t=1719860

As a point of comparison, here is a log of mine - check out the MAF curve; much smoother without those "oscillations." I am on stock intake with a drop in filter.
https://datazap.me/u/thejeremyman9/4...0&data=4-19-25

That is fascinating for sure. Yeah it looks like our MAF readings are very similar with how they bounce. Funny that we both have the Dinan Intake as well. I do still have factory intake with drop in as well as the M performance intake bottom. May throw one of those back on and see what happens. I do have the small AFE Air scoop installed behind the grill as well but dont know if that could cause any of the turbulance.

Your MAF reading is very linear and solid.

[thejeremyman9]

Originally Posted by ozymandias435

That is fascinating for sure. Yeah it looks like our MAF readings are very similar with how they bounce. Funny that we both have the Dinan Intake as well. I do still have factory intake with drop in as well as the M performance intake bottom. May throw one of those back on and see what happens. I do have the small AFE Air scoop installed behind the grill as well but dont know if that could cause any of the turbulance.

Your MAF reading is very linear and solid.

Swapping back to the stock intake would be an interesting experiment on the MAF readings, do log and post if you try that.

[ozymandias435]

Originally Posted by thejeremyman9

Swapping back to the stock intake would be an interesting experiment on the MAF readings, do log and post if you try that.

Pulled the 2nd plug and measured and it measured to .026. There lies the problem. Gapped that one down to where it should be. All the other plugs are .022. Swapped the first and second coil anyway as well.

Swapped out the Dinan CAI for the factory M performance top with drop in filter. Still a closed system.

Went and just did another log:
https://www.bootmod3.net/log?id=5ec3...729b5c747a1dde

-2 Cyl timing cleared up
-MAF still bouncing and it appears stock airbox flows less in lower RPMs
Also is that MAF low for FBO + Fabspeed Sport Cat + Pure Inlet + BM3 Stg 2?? Feel like I see a lot of other logs that are getting up to 40.

I really wonder if the AFE Ram scoop is causing the turbulence

[thejeremyman9]

Originally Posted by ozymandias435

Pulled the 2nd plug and measured and it measured to .026. There lies the problem. Gapped that one down to where it should be. All the other plugs are .022. Swapped the first and second coil anyway as well.

Swapped out the Dinan CAI for the factory M performance top with drop in filter. Still a closed system.

Went and just did another log:
https://www.bootmod3.net/log?id=5ec3...729b5c747a1dde

-2 Cyl timing cleared up
-MAF still bouncing and it appears stock airbox flows less in lower RPMs
Also is that MAF low for FBO + Fabspeed Sport Cat + Pure Inlet + BM3 Stg 2?? Feel like I see a lot of other logs that are getting up to 40.

I really wonder if the AFE Ram scoop is causing the turbulence

I guess ours thoughts were on point with plug #2 then .

Interesting that it flows less at lower RPM? I honestly dont pay much attention to the actual MAF values themselves, but i do recall other people maxing out the MAF with BM3 stage 2 FBO? Might be worth looking at other logs in the BM3 thread to see.

I thought about the scoop also... i guess its easy to test. You would expect the filter to dampen that turbulence, if any, especially with how much air the engine is sucking at WOT. (In other words i dont think the scoop is actually producing positive pressure at the MAF; i think you are sucking in more air than it is "scooping")

[ozymandias435]

Originally Posted by thejeremyman9

I guess ours thoughts were on point with plug #2 then .

Interesting that it flows less at lower RPM? I honestly dont pay much attention to the actual MAF values themselves, but i do recall other people maxing out the MAF with BM3 stage 2 FBO? Might be worth looking at other logs in the BM3 thread to see.

I thought about the scoop also... i guess its easy to test. You would expect the filter to dampen that turbulence, if any, especially with how much air the engine is sucking at WOT. (In other words i dont think the scoop is actually producing positive pressure at the MAF; i think you are sucking in more air than it is "scooping")

Checking out a bunch of other logs and almost everyone gets to 40 or maxes out at 41.4. Wonder why I am stuck at 35ish. About to throw the Dinan back on and remove the scoop and drive it tomorrow to see how she feels.

And again thank you for all of your help my man

[ozymandias435]

Originally Posted by thejeremyman9

I guess ours thoughts were on point with plug #2 then .

Interesting that it flows less at lower RPM? I honestly dont pay much attention to the actual MAF values themselves, but i do recall other people maxing out the MAF with BM3 stage 2 FBO? Might be worth looking at other logs in the BM3 thread to see.

I thought about the scoop also... i guess its easy to test. You would expect the filter to dampen that turbulence, if any, especially with how much air the engine is sucking at WOT. (In other words i dont think the scoop is actually producing positive pressure at the MAF; i think you are sucking in more air than it is "scooping")

Removed the scoop, removed the Pure Inlet, installed brand new factory inlet, reinstalled Dinan CAI.

Just did a log and hit 45.3 Peak MAF reading. Thats 10 higher than my peak from yesterdays logs. 10 higher is pretty insane

Was having a hard time getting the Pure to seal to either the Dinan or the Factory Inlet....the pure actually sat inside the mouth of both instakes and there was some space around it that probably was creating a small leak.

On top of that maybe the scoop was creating that crazy turbulance?

Todays Log
https://www.bootmod3.net/log?id=5ec4...0b431d55ba8756

[thejeremyman9]

Originally Posted by ozymandias435

Removed the scoop, removed the Pure Inlet, installed brand new factory inlet, reinstalled Dinan CAI.

Just did a log and hit 45.3 Peak MAF reading. Thats 10 higher than my peak from yesterdays logs. 10 higher is pretty insane

Was having a hard time getting the Pure to seal to either the Dinan or the Factory Inlet....the pure actually sat inside the mouth of both instakes and there was some space around it that probably was creating a small leak.

On top of that maybe the scoop was creating that crazy turbulance?

Todays Log
https://www.bootmod3.net/log?id=5ec4...0b431d55ba8756

So, it sounds like you very likely had a vacuum leak at the inlet to intake connection with the pure on. That was letting in unmetered air and lowering your MAF readings. The thing that is interesting is that the leak seemed big (in terms of lowering the MAF readings significantly), but looking back at the old logs, your STFT was barely over 1, so there didn't seem to be a lot of correction for letting in unmetered air with the leak... Maybe the fuel calculations are not super sensitive to MAF readings.

It's hard to say whether it was the scoop or the leak causing some buffeting or instability at the MAF since you changed both at the same time. I guess if you really wanted to know you could reinstall the scoop now and see how it affects the magnitude of the MAF readings and the curve.

EDIT: Also looks like you had a few degrees of timing pulled from 4 cylinders up top.

[ozymandias435]

Originally Posted by thejeremyman9

So, it sounds like you very likely had a vacuum leak at the inlet to intake connection with the pure on. That was letting in unmetered air and lowering your MAF readings. The thing that is interesting is that the leak seemed big (in terms of lowering the MAF readings significantly), but looking back at the old logs, your STFT was barely over 1, so there didn't seem to be a lot of correction for letting in unmetered air with the leak... Maybe the fuel calculations are not super sensitive to MAF readings.

It's hard to say whether it was the scoop or the leak causing some buffeting or instability at the MAF since you changed both at the same time. I guess if you really wanted to know you could reinstall the scoop now and see how it affects the magnitude of the MAF readings and the curve.

I feel like the scoop may have been causing the turbulence and the vacuum leak was causing the low MAF readings. Thanks again for your help and opinions. Now to get rid of this rough idle I've picked up since deleting the cold start lol

I did notice the timing pulled as well. Im switching to new factory coils tomorrow. Going to check the other 5 plugs as well and make sure they are gapped correctly. Have not been impressed with these coils I installed last Friday