Rich AFR Bank 1 on Decel

DavN54

New Member
Nov 9, 2022
6
1
0
Hello all, hoping someone can help!

I’ve searched through every N54 forum or community for my issue but really nothing conclusive or logical

To keep it simple, my AFR1 and AFR2 readings aren’t the same on deceleration. AFR2 will go full lean (234) relatively quickly but my AFR1 will lag behind for quite a few seconds around the 180-210 figure.

So the first suspicion would be injectors, but I’ve changed them 6 months ago so it felt unlikely. I’ve let the car sit overnight and checked the plugs and only cylinder 2 plug was somewhat black and fouled on the threads but not the electrode. I’ve swapped injector on cylinder 2 with cylinder 4 on bank 2 with no change. I could swap the other injectors but I highly doubt this is the issue. For all the other similar threads posted it rarely ended up being the injectors.

My O2 readings both pre and post cats look good on INPA with symmetrical voltage readings and error free testing. My LTFTs look within range (10% max difference between both banks). Car actually runs fine with no errors.

The confusing part is that I’ve checked three logs done 1) pre new injectors 2) after new injectors 3) recently and this delta in AFR readings on deceleration is consistent all the time. In 1) the injectors actually where leaking with a lot of misfire codes and obvious fuel leak into the exhaust.

Afaik AFR readings are measured by O2 sensors, I’ve ordered a new pre and post cat set to see if maybe they’re faulty. Clearing lambda adaptions on MHD did nothing for me. I suspect this won’t change much.

Alternatively, one could assume faulty valve seals but compression on all cylinders is 175psi, so I doubt there’s an oil leak in here.

One guy fixed it by replacing a cracked valve cover gasket, but after inspection I see no seepage. Coil and plug holes look ok except a bit of carbon sediment at the bottom which I believe is normal. Even the injector holes are clean and look round, so I doubt there’s any issue here. Unless there’s an internal leak in the VCG I’m not seeing, but would like to hear some suggestions on this. Car has 60.000km 2010 Z4, so low end of mileage doesn’t make this very probable.

Another guy fixed it by changing faulty turbos, but his were leaking and had only issue when getting into boost. I have a set of hybrids to install due to turbo siren on stockers, but even here, I don’t have high hopes that this will fix it.

Here’s a log link from a highway run https://datazap.me/u/davgia/ggh?log=0&data=13-14-20

I rarely tend to post unless really necessary but I’ve exhausted reading material on the matter..

Any input is absolutely appreciated,
Cheers,
Dave
 

ajoosten

New Member
Mar 26, 2018
6
0
0
Ride
135i
Hello all, hoping someone can help!

I’ve searched through every N54 forum or community for my issue but really nothing conclusive or logical

To keep it simple, my AFR1 and AFR2 readings aren’t the same on deceleration. AFR2 will go full lean (234) relatively quickly but my AFR1 will lag behind for quite a few seconds around the 180-210 figure.

So the first suspicion would be injectors, but I’ve changed them 6 months ago so it felt unlikely. I’ve let the car sit overnight and checked the plugs and only cylinder 2 plug was somewhat black and fouled on the threads but not the electrode. I’ve swapped injector on cylinder 2 with cylinder 4 on bank 2 with no change. I could swap the other injectors but I highly doubt this is the issue. For all the other similar threads posted it rarely ended up being the injectors.

My O2 readings both pre and post cats look good on INPA with symmetrical voltage readings and error free testing. My LTFTs look within range (10% max difference between both banks). Car actually runs fine with no errors.

The confusing part is that I’ve checked three logs done 1) pre new injectors 2) after new injectors 3) recently and this delta in AFR readings on deceleration is consistent all the time. In 1) the injectors actually where leaking with a lot of misfire codes and obvious fuel leak into the exhaust.

Afaik AFR readings are measured by O2 sensors, I’ve ordered a new pre and post cat set to see if maybe they’re faulty. Clearing lambda adaptions on MHD did nothing for me. I suspect this won’t change much.

Alternatively, one could assume faulty valve seals but compression on all cylinders is 175psi, so I doubt there’s an oil leak in here.

One guy fixed it by replacing a cracked valve cover gasket, but after inspection I see no seepage. Coil and plug holes look ok except a bit of carbon sediment at the bottom which I believe is normal. Even the injector holes are clean and look round, so I doubt there’s any issue here. Unless there’s an internal leak in the VCG I’m not seeing, but would like to hear some suggestions on this. Car has 60.000km 2010 Z4, so low end of mileage doesn’t make this very probable.

Another guy fixed it by changing faulty turbos, but his were leaking and had only issue when getting into boost. I have a set of hybrids to install due to turbo siren on stockers, but even here, I don’t have high hopes that this will fix it.

Here’s a log link from a highway run https://datazap.me/u/davgia/ggh?log=0&data=13-14-20

I rarely tend to post unless really necessary but I’ve exhausted reading material on the matter..

Any input is absolutely appreciated,
Cheers,
Dave
Dave,

Have you had any luck solving this issue?
 

DavN54

New Member
Nov 9, 2022
6
1
0
Dave,

Have you had any luck solving this issue?

Not yet, cars been stored for winter

Soon I will troubleshoot with the following:
- New pre and post cat O2 sensors
- New TTE500 Turbos

As what I have tried in the meanwhile with no effect:
- New valve cover and gasket
- Reset all adaptions with MhD and protool
- Swapped Injectors with no difference
- Tried techron equivalent injector cleaner

Car doesn’t have excessive smoking, so that points way from PVC problem or valve stem seal issue (idling it for 15 minutes and then accelerating doesn’t produce a cloud of smoke). Some soot from the exhaust on start up present, but that could be from the OTS tune running rich.

So yeah, hoping it’s faulty O2 sensors (potentially fouled by bad injectors I replaced shortly after purchasing car) or bad turbo seal leaking small amount oil in the exhaust. My turbos have pretty audible turbo siren (inlets sealing fine), so I guess it’s that.

If all of this doesn’t fix it, I will have no idea 🤷‍♂️
 

ajoosten

New Member
Mar 26, 2018
6
0
0
Ride
135i
Not yet, cars been stored for winter

Soon I will troubleshoot with the following:
- New pre and post cat O2 sensors
- New TTE500 Turbos

As what I have tried in the meanwhile with no effect:
- New valve cover and gasket
- Reset all adaptions with MhD and protool
- Swapped Injectors with no difference
- Tried techron equivalent injector cleaner

Car doesn’t have excessive smoking, so that points way from PVC problem or valve stem seal issue (idling it for 15 minutes and then accelerating doesn’t produce a cloud of smoke). Some soot from the exhaust on start up present, but that could be from the OTS tune running rich.

So yeah, hoping it’s faulty O2 sensors (potentially fouled by bad injectors I replaced shortly after purchasing car) or bad turbo seal leaking small amount oil in the exhaust. My turbos have pretty audible turbo siren (inlets sealing fine), so I guess it’s that.

If all of this doesn’t fix it, I will have no idea 🤷‍♂️
 

ajoosten

New Member
Mar 26, 2018
6
0
0
Ride
135i
I’m in a similar boat with floating AFRs on decel. My car has been sitting for a while and I have tried a bunch of things. I have swapped injectors around, changed out O2 sensors, verified no excess crank case pressure. I have some random smoke at idle and decel. I am running pure stage 2 turbos that only have a few thousand miles on them. My oil consumption is high with no external leaks.

I assume you coded the new I injectors when installing?
So you have any oil leaks around the exterior of the turbo cassette clamps?
How quick are you consuming oil? Is there smoke on hard decel?
Is there smoke on a hard down shift at high rpm?
Do you find a lot of liquid in your low side catch can?
Do you have a vacuum break on your pcv system?
Is there any way to get fresh air in the crankcase?
 

DavN54

New Member
Nov 9, 2022
6
1
0
I’m in a similar boat with floating AFRs on decel. My car has been sitting for a while and I have tried a bunch of things. I have swapped injectors around, changed out O2 sensors, verified no excess crank case pressure. I have some random smoke at idle and decel. I am running pure stage 2 turbos that only have a few thousand miles on them. My oil consumption is high with no external leaks.

I assume you coded the new I injectors when installing?
So you have any oil leaks around the exterior of the turbo cassette clamps?
How quick are you consuming oil? Is there smoke on hard decel?
Is there smoke on a hard down shift at high rpm?
Do you find a lot of liquid in your low side catch can?
Do you have a vacuum break on your pcv system?
Is there any way to get fresh air in the crankcase?
I’m in the process of getting a two post lift installed and as soon as that is done I will get straight into installing the new turbos and exchanging all four o2 sensors

Haven’t driven the car too much lately so can’t say for certain if there is any smoking issue on hard decel or if there is excessive oil consumption. Definitely no oil leaks anywhere, been under the car for quite a while and would have noticed.

Swapped and coded injectors both with INPA and ProTool. No catch can for now.

Have you tried idling the car for 15 minutes and then pressing the accelerator to see if a thick cloud of smoke comes out?
 

carabuser

Lieutenant
Oct 2, 2019
881
1
778
0
UK
Ride
Z4 35i & 335i
Looks like a perfect example of leaking injectors to me. The way the afrs lazily return to 254 is textbook and the soot out the exhaust on startup.

You mentioned that they were replaced, but is it possible they are fakes or refurbished units?

Before changing turbos and O2s it would be worth checking the injectors visually while under pressure.
 

DavN54

New Member
Nov 9, 2022
6
1
0
Looks like a perfect example of leaking injectors to me. The way the afrs lazily return to 254 is textbook and the soot out the exhaust on startup.

You mentioned that they were replaced, but is it possible they are fakes or refurbished units?

Before changing turbos and O2s it would be worth checking the injectors visually while under pressure.

- New, sealed and capped injectors with varying serial codes from reputable bmw spare parts vendor (leebman)

- Swapped them between banks, swapped them randomly, tried new seals and clips with appropriate seal compression tool, checked bore for play. Nada..

- If they cost as little as B58 injectors I’d be tempted to buy a whole new set of 6… but understandably at 2.5/3k a set, there’s no appetite for it, especially with no guarantee of fixing the issue

Im pbondars yellow Z4 twin btw, we’ve discussed it before on WA.. Radio silence on progress is me waiting on vendor delivering and installing that damn two post lift!
 
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ajoosten

New Member
Mar 26, 2018
6
0
0
Ride
135i
I have fixed my lazy O2 sensors for now. Flashed back to MHD stock map. Filled up with 93 octane (normally run E85) and drove for 30 min at high rpm to get everything as hot as possible. With dual oiler coolers it is hard to get above 230F. Reset all of the codes with ISTA/ICOM(BMW software and interface), uploaded custom MHD tune again. Reset ever adaptation on MHD. Went for a drive to fill back up with E85. Logged and now they are working. The computers on this car have tricked me multiple times, where they have been the issue. There is some magic that happens with the BMW ISTA software through the proper ICOM interface. If you have someone that has the ICOM/ISTA interface I would give that a shot. I don’t know that was the fix but previous experience would lead me to believe that was it.