[eastsidaz]

Originally Posted by Aria335iN54

Right so I assume you got good results with running n55 plugs, I might give them a shot later.

Other than that I can't think of anything else causing this issue.
I know these engines are prone to cam ledges wear so maybe that is slowly happening and causing some minor issues without triggering codes but who knows...

Whats your current plugs? I have the 3-prong ZGR6STE2

[Aria335iN54]

Originally Posted by GovernUrMental

Whats your current plugs? I have the 3-prong ZGR6STE2

NGK-97968 gapped .022
They are very common on n54 platform so unlikely to be cause of this issue

[eastsidaz]

Originally Posted by CarAbuser

ZR5TPP33 Gapped to 0.022" and Bosch coils.

Are those N55 spark plugs longer than n54?

[CarAbuser]

Originally Posted by GovernUrMental

Are those N55 spark plugs longer than n54?

I didn't measure them but they looked the same size as the 5992s they replaced.

[gster109]

What a coincidence, I was coming on the forums to ask this exact same question !

I am catless as well & what I've heard on this subject is that as long as the afr's are about .2 of each other then it's perfectly fine. They should always be in sync w about .2 deviation.
In regards to the fluctuations I get the exact same behavior (13.9-15ish) 13 & 15 come on for split seconds then get back into the 14 range & im on brand new index 12's & 2 step colder plugs.

[Aria335iN54]

Originally Posted by gster109

What a coincidence, I was coming on the forums to ask this exact same question !

I am catless as well & what I've heard on this subject is that as long as the afr's are about .2 of each other then it's perfectly fine. They should always be in sync w about .2 deviation.
In regards to the fluctuations I get the exact same behavior (13.9-15ish) 13 & 15 come on for split seconds then get back into the 14 range & im on brand new index 12's & 2 step colder plugs.

How are your deceleration fuel cut afrs look like?
Do they jump to and remain at 234.95 as they are supposed to or fluctuate near 234.95 sometimes like mine?

I wonder if these two issues of mine are linked.

[eastsidaz]

Originally Posted by Aria335iN54

How are your deceleration fuel cut afrs look like?
Do they jump to and remain at 234.95 as they are supposed to or fluctuate near 234.95 sometimes like mine?

I wonder if these two issues of mine are linked.

Both of mine cut off at the same time. So doesn't seem to be the issue.

Can you share actual log?

[Aria335iN54]

Originally Posted by GovernUrMental

Both of mine cut off at the same time. So doesn't seem to be the issue.

Can you share actual log?

Idle log

https://datazap.me/u/pirouz/n54-rear-o2-connected?log=0&data=3-20

Deceleration log

https://datazap.me/u/pirouz/n54-cruising-log

Did I mention when I disconnect rear O2 idle afrs become super smooth which indicates the issue is triggered by fluctuating rear O2 signals.
Tried with new Bosch and NTK o2s same problem.


I wonder if its got something to do with vanos/cam injection/ignition timing

[Renzke]

Check with INPA if learning bits are set. In MSD80/81 main menue: F5/Shift+F6/F3 "Lernbits für Injektoren Balancing", Line 1,2,4 should be colored. If not the car will be not able reach a perfect idle / AFR ratio. Anyway in this case there is a reason for it.
As you mentioned your car AFR was perfect with rear O2's disconnected check the connection of midpipe to downpipe in cold start condition with soapy water for exhaust leaks. The N54 regulation is really sensitive.
Furthermore delete all adaptions (MSD80/81 main menue: F8/F2/Shift+F9 "MSD Adaptionene selektiv löschen"). This may solve some problems as well.
Besides this there are for sure lots of possiblities.

I'm having equal issues as well and going thru the whole process.
I had a gasket leak in bank 2 and above that maybe one of my injectors in bank 1 is bad (all Ind. 12, new spark plugs & coils, new wideband lambdas, bank 1 AFR always slightly behind bank 2 AFR when jumping to 234,95 / releasing the acc. pedal).

Inpa MSD80/81 loader version: 2.023. The sequence (Fx/ShiftFx/...) may be different with another version (Version is visible when in MSD80/81 main menue on top of the window).

[Aria335iN54]

Originally Posted by Renzke

Check with INPA if learning bits are set. In MSD80/81 main menue: F5/Shift+F6/F3 "Lernbits für Injektoren Balancing", Line 1,2,4 should be colored. If not the car will be not able reach a perfect idle / AFR ratio. Anyway in this case there is a reason for it.
As you mentioned your car AFR was perfect with rear O2's disconnected check the connection of midpipe to downpipe in cold start condition with soapy water for exhaust leaks. The N54 regulation is really sensitive.
Furthermore delete all adaptions (MSD80/81 main menue: F8/F2/Shift+F9 "MSD Adaptionene selektiv löschen"). This may solve some problems as well.
Besides this there are for sure lots of possiblities.

I'm having equal issues as well and going thru the whole process.
I had a gasket leak in bank 2 and above that maybe one of my injectors in bank 1 is bad (all Ind. 12, new spark plugs & coils, new wideband lambdas, bank 1 AFR always slightly behind bank 2 AFR when jumping to 234,95 / releasing the acc. pedal).

Inpa MSD80/81 loader version: 2.023. The sequence (Fx/ShiftFx/...) may be different with another version (Version is visible when in MSD80/81 main menue on top of the window).

Do you also have idle afr excessive oscillation?

I have inpa loader 5 and can't find those options but have already done All Adaptions reset.

For decel afr common causes people report apart from injectors are valve cover vac leak or turbo oil leak affecting O2s.
I have already replaced both plus any other part which can impact air and fuel.
I am just gonna find a used throttle and replace as the last resort before I get into the valvetrain and check cam ledges and lifters etc ...

[gster109]

Originally Posted by Aria335iN54

How are your deceleration fuel cut afrs look like?
Do they jump to and remain at 234.95 as they are supposed to or fluctuate near 234.95 sometimes like mine?

I wonder if these two issues of mine are linked.

I believe these are separate issues you're talking about, Just got fresh index 12's and they jump to 234.95 on decel in gear.

The AFR's fluctuating are weird, experiencing these myself I'm in the process of doing my Valve Cover because there was a micro fracture on the oil fill cap. Hopefully that solves the issue, saw that you mentioned that might be one of the reasons the fluctuations could happen.

[gster109]

Originally Posted by Aria335iN54

Do you also have idle afr excessive oscillation?

I have inpa loader 5 and can't find those options but have already done All Adaptions reset.

For decel afr common causes people report apart from injectors are valve cover vac leak or turbo oil leak affecting O2s.
I have already replaced both plus any other part which can impact air and fuel.
I am just gonna find a used throttle and replace as the last resort before I get into the valvetrain and check cam ledges and lifters etc ...

Could Cam Ledges cause Idle AFR Fluctuations like that???

[CarAbuser]

If your AFR oscillations look like the attached picture then it's caused by the catalyst diagnostic routine. The ECU adds extra fuel to 1 bank and removes some from the other and then swaps this around which creates that helix looking pattern in the 2 AFR readings.

It's only really a problem on catless cars as the routine won't complete. You can stop this behaviour by tweaking the DME tune.

[Sgop335]

Originally Posted by GovernUrMental

Are those N55 spark plugs longer than n54?

Yes they stick more into the cc compared to stock say 2mm or so

[eastsidaz]

Originally Posted by CarAbuser

If your AFR oscillations look like the attached picture then it's caused by the catalyst diagnostic routine. The ECU adds extra fuel to 1 bank and removes some from the other and then swaps this around which creates that helix looking pattern in the 2 AFR readings.

It's only really a problem on catless cars as the routine won't complete. You can stop this behaviour by tweaking the DME tune.

Yeah i came to the conclusion that it's normal.

Found some info https://www.meeknet.co.uk/E38/Diagnostics.htm

RAW output from the Lambda sensor BEFORE the catalytic converter. This is a measurement of the remaining Oxygen in the exhaust gasses and indicates the fuel/air mixture before combustion
This (should) constantly change in voltage (0.2V - 0.9V) <This from the narrow band sensors it what causes the fluctuations

So can this be disabled at all? Or only reduced in tune?

[Aria335iN54]

Originally Posted by CarAbuser

If your AFR oscillations look like the attached picture then it's caused by the catalyst diagnostic routine. The ECU adds extra fuel to 1 bank and removes some from the other and then swaps this around which creates that helix looking pattern in the 2 AFR readings.

It's only really a problem on catless cars as the routine won't complete. You can stop this behaviour by tweaking the DME tune.

Right I am on MHD OTS tunes and also asked them about this idle fluctuations and they had no idea !

Is it possible that they totally missed addressing this issue in their catless tunes ?
So perhaps that check box for catless downpipes in mhd flash options does not really do much apart from stopping the catless engine fault light

I assume custom tune is the only solution then?

[eastsidaz]

Originally Posted by Sgop335

Yes they stick more into the cc compared to stock say 2mm or so

I just looked it up they all seem to be the same reach

N54 plugs ZGR6STE2 Reach 26.5mm
N55 plugs ZR5TPP33 Reach 26.5mm
One step colder NGK ILZKBR7B8G Reach 26.5mm

[Sgop335]

Originally Posted by GovernUrMental

I just looked it up they all seem to be the same reach

N54 plugs ZGR6STE2 Reach 26.5mm
N55 plugs ZR5TPP33 Reach 26.5mm
One step colder NGK ILZKBR7B8G Reach 26.5mm

Dont want to start spark plug 101. Reach is the length of the threaded section only. Then you have the projection, gap and ground electrode.
The Zr5tpp33 has a T in it compared to S for the stock.
T is 7mm projection.
S is 5.

[CarAbuser]

Yes it can be tuned out but a custom tune is needed. It should be standard on any catless tune but I don't think many people notice so that's probably why MHD haven't looked into it and adjusted the OTS maps.

I noticed it on logs for my car so did some research and made some changes to stop the afr oscillations. I was getting them at idle and when cruising between 50 an 70.

[eastsidaz]

Originally Posted by CarAbuser

Yes it can be tuned out but a custom tune is needed. It should be standard on any catless tune but I don't think many people notice so that's probably why MHD haven't looked into it and adjusted the OTS maps.

I noticed it on logs for my car so did some research and made some changes to stop the afr oscillations. I was getting them at idle and when cruising between 50 an 70.

Excellent! I'm interested to know what changes were done? I run my own tune but switch to mhd sometimes.

[Aria335iN54]

Originally Posted by CarAbuser

Yes it can be tuned out but a custom tune is needed. It should be standard on any catless tune but I don't think many people notice so that's probably why MHD haven't looked into it and adjusted the OTS maps.

I noticed it on logs for my car so did some research and made some changes to stop the afr oscillations. I was getting them at idle and when cruising between 50 an 70.

That's good finding man.
1000s of people are on mhd catless tunes and only few have noticed this issue!

If you have any reference links docs to share would be good.
I might start hassling mhd again...

[Aria335iN54]

Originally Posted by GovernUrMental

I just looked it up they all seem to be the same reach

N54 plugs ZGR6STE2 Reach 26.5mm
N55 plugs ZR5TPP33 Reach 26.5mm
One step colder NGK ILZKBR7B8G Reach 26.5mm

Those bosch plugs are a bit taller same as ngk 2 step colder plugs.

I just installed them and they helped a lot with cold start splutters.
I never had perfect cold start with ngk plugs.

However they did not help with the ideal afr issue if that's what you after