Afr on decel

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Oct 28, 2017
818
Monroe CT
#1
I always went straight to 234 on decel in my lambdas with my old injectors ,i recently updated to index 12 and they used to do the same. I found a crack in my valve cover and fixed with epoxy while im waiting for new one. I also ordered new plugs and the new black r8 coils that panzer showed us. So I setup my logging tablet and neither of my lambdas close out steady on deceleration. Bank 2 hits 234 randomly but bank 1 hovers around 200 , does anyone have any clue how this is or could multiple index 12 injectors from I buy auto parts have shit the bed in 3k miles.
 
Oct 28, 2017
818
Monroe CT
#3
Decel should read full lean, "Fuel Cut On Decel".

Are you sure you're diagnosing bad injectors correctly?

I have to go through this myself to learn it (it's not N54 specific, but DME is similar). It's the most thorough walk through I've found.

https://bimmerprofs.com/microparticle-in-the-injector/
My old injectors were good in replaced them with index 12 to be preventative and to get ready for bigger turbos. And full lean on our dme is 234. Something that's why I know something is wrong but for both banks to have a brand new injector go is odd. That's why i am trying to see what it could be .
 

langsbr

Lieutenant
Apr 5, 2017
707
#4
I haven't used it yet, but someone mentioned INPA has a "rough idle" test I think that can help diagnose bad injectors. It is definitely odd to have both banks acting up, but if all other parts are functional, e.g. O2s, wiring, etc. it stands to reason that there is a tiny leak in an injector in both banks. How are the STFT when runing WOT? Everything inline with how it was pre-injector swap?
 
Oct 28, 2017
818
Monroe CT
#5
I haven't used it yet, but someone mentioned INPA has a "rough idle" test I think that can help diagnose bad injectors. It is definitely odd to have both banks acting up, but if all other parts are functional, e.g. O2s, wiring, etc. it stands to reason that there is a tiny leak in an injector in both banks. How are the STFT when runing WOT? Everything inline with how it was pre-injector swap?
It was always good except recently with new Injectors I had a deviation at high rpm on wot after I brought the car in for a recall. Turned out they never clamped one of my inlets and I have a crack on valve cover. I cant say the valve cover was from dealer but the inlet def was. Either way now my trims are perfect.
 
Oct 28, 2017
818
Monroe CT
#6
Dec 1, 2016
197
New York
#8
I have an N55 so only 1 "bank," but, AFR always settled to 235 until I started having an injector issue. AFR started hanging around 200 and/or bouncing off 235. Replaced injector 2 and 6 (plugs looked to be too rich) and now it settles back to 235 quickly and stays there. I'd pull the plugs and see if you have any that look wet and/or fouled.
 

Twisted Tuning

Lieutenant
Platinum Vendor
Oct 25, 2016
747
New York
#10
You have a leaking injector(s). this is what I've told customers to do when looking for injector issues. has worked 9 out 10 times to find leaking injectors......


Put car in 2nd or 3rd gear. Bring rpms up to like 5000rpms preferably going down a slight hill. Once up to 5k....just let off the pedal and let the car decelerate in gear until like 2000-2500rpm

Use manual logging for that.


What you have already seen is what you will see on this test. Unfortunately it wont tell you which one It is. but can narrow it down to which bank.
 
Oct 28, 2017
818
Monroe CT
#11
You have a leaking injector(s). this is what I've told customers to do when looking for injector issues. has worked 9 out 10 times to find leaking injectors......


Put car in 2nd or 3rd gear. Bring rpms up to like 5000rpms preferably going down a slight hill. Once up to 5k....just let off the pedal and let the car decelerate in gear until like 2000-2500rpm

Use manual logging for that.


What you have already seen is what you will see on this test. Unfortunately it wont tell you which one It is. but can narrow it down to which bank.
Could a cracked valve cover cause this as well cause it's just weird that 2 weeks ago my logs are fine I get this crack and all of sudden I get leaking injectors on both banks when the injectors are 6 months old. Also when the car is cold seems they close and hit 234 still do it slow but they do. I just would like to do warranty claim asap but don't want to if it's not my injectors.
 
Dec 1, 2016
197
New York
#12
Could a cracked valve cover cause this as well cause it's just weird that 2 weeks ago my logs are fine I get this crack and all of sudden I get leaking injectors on both banks when the injectors are 6 months old. Also when the car is cold seems they close and hit 234 still do it slow but they do. I just would like to do warranty claim asap but don't want to if it's not my injectors.
The injectors I just replaced actually showed the same symptoms... On a cold start AFR settled to 235 fine (usually). As the car warmed up, or I did a pull, I would see AFR not settling...

I'd think a cracked valve cover would result in un-metered airflow and a lean condition, no? AFR not settling to 235 would mean that the sensor is seeing more parts fuel in the exhaust mixture than expected.
 
Oct 28, 2017
818
Monroe CT
#13
The injectors I just replaced actually showed the same symptoms... On a cold start AFR settled to 235 fine (usually). As the car warmed up, or I did a pull, I would see AFR not settling...

I'd think a cracked valve cover would result in un-metered airflow and a lean condition, no? AFR not settling to 235 would mean that the sensor is seeing more parts fuel in the exhaust mixture than expected.
I didn't know if oil could be getting into combustion chamber through head ports
 

Twisted Tuning

Lieutenant
Platinum Vendor
Oct 25, 2016
747
New York
#14
Could a cracked valve cover cause this as well cause it's just weird that 2 weeks ago my logs are fine I get this crack and all of sudden I get leaking injectors on both banks when the injectors are 6 months old. Also when the car is cold seems they close and hit 234 still do it slow but they do. I just would like to do warranty claim asap but don't want to if it's not my injectors.
I didn't know if oil could be getting into combustion chamber through head ports

Im not sure that a cracked VC would cause a rich condition on Decel. being N54, and if your head ports are not plugged. a VC crack in the right place would induce a lean condition by sucking in air through the VC and into the head ports. and if oil caused a rich condition, i would say you had other issues like bad oil/fuel dilution. do you have PI or any type of secondary fueling? PI or leaking meth systems can cause AFR not to settle on Decel as well.
 
Oct 28, 2017
818
Monroe CT
#15
Im not sure that a cracked VC would cause a rich condition on Decel. being N54, and if your head ports are not plugged. a VC crack in the right place would induce a lean condition by sucking in air through the VC and into the head ports. and if oil caused a rich condition, i would say you had other issues like bad oil/fuel dilution. do you have PI or any type of secondary fueling? PI or leaking meth systems can cause AFR not to settle on Decel as well.
No other fuel source the only other thing that changed was going to biosyn 5w30 oil. If I decel for a while I can get it to settle at 234 on both banks but bank 1 still takes longer. Also it seems if I am running boost then let off that I have a much better chance of it hitting 234 much quicker. Still not normal but def quicker. I would just think if their is an internal crack in valve cover it could mess with pcv and oil vapors could affect things but i only have 500 miles on this oil so I hoping their isn't that much fuel and also I have had leaking injectors on previous cars. This car starts and runs perfect and it should be horrible multiple leaks so either buy auto parts sold me crap that was supposed to be new it is something else. I'm hoping for the latter cause I dont want to get another set of the same from them and I already spent g with them don't want spend 1500 to 2000 for no reason but don't want to keep changing injectors as I don't like messing with stuff like that more than nec.
 

Hydra Performance

Corporal
Platinum Vendor
Jan 31, 2017
154
#17
@Rob09msport
Could it be that your lambdas are aged? O2 sensors usually get slower with age, and are best replaced after the 100,000mi mark... Just a thought.
 
Oct 28, 2017
818
Monroe CT
#18
@Rob09msport
Could it be that your lambdas are aged? O2 sensors usually get slower with age, and are best replaced after the 100,000mi mark... Just a thought.
Yes they are original and no cats cant help I was planning on changing them when I Install your turbos as I have been replacing everything in preparation for this. I didnt know if bad o2 sensors would read like that.
Edit I have 70k miles on my car so they are due. Can I check voltages or anything with inpa? I should get a 234 reading with the car off as well to correct?
 
Jul 27, 2017
150
#19
may be a stupid question but you haven't enabled the burble mod have you? (Which squirts in fuel for pops and bangs.)
 
Oct 28, 2017
818
Monroe CT
#20
may be a stupid question but you haven't enabled the burble mod have you? (Which squirts in fuel for pops and bangs.)
Not stupid at all many make that mistake but I don't use burbles I don't see benefit to it. Now shift farts those would be amazing if we could flash spark cut for torque reduction instead of timing lol
 

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