S6 C6 Mysterious Misfiring

[dopiata]

I agree with all of your statements … and the shim fix on the TSB sounds suspect … plus it is an alum spring seat … which I can only assume would eventually marry to the head … I have cyl 5+6 misfire periodically … it all depends how I drive the car … and believe the issue is either the coils are not hot enough or the plugs … or the real cause is the springs and floating at higher rpms and boost.

That said … next week, I am going to have all the fluids replaced, and need the rear diff fluid checked … at this time … I will go over with the mech all my future plans for the car … and this is what I sum it up as.

NOTE: I have an ARP tune but am missing the dongle … so I will want this as well.

Stainless Braided Turbo Oil Line and Strainer/Screen Relocation Kit - C7 S6-S7-RS7, D4 A8-S8 4.0T
SKU JHM-079115175G-TSB-2044640
Manufacturer: JHM
$549.95

APR Valve Springs/Seats/Retainers - Set Of 32
Manufacturer: ARP
$1,300 (approx)

APR RED IGNITION COIL 8 PACK WITH SPARK PLUGS (NGK R7437-8) (NGK R7437-9)
SKU MS100219-PLUG-8PK
$703.52

APR recommends NGK heat range 9 (NGK-R7437-9) spark plugs gapped to 0.024" ±0.002" or 0.6mm ±0.05mm with a change interval of 10-15,000 mi

APR Mobile Bluetooth Dongle
SKU EM100032
$220.95

My question is the following … and please respond if you know the ans.

If I want to have a display system like the Edge CTS3 (Insight) … which I have in my diesel truck … are there any manufacturers that have such a system that is plug in … and can show me the display like an Edge?

[kvn]

Hi, so I did a little trip just now, and took notes of LTFT and STFT. Was hoping for your wisdom and opinion.
ECM1 LSFT:

ECM2 LSFT:

Misfire range:

The STFT was during warm idle between 0 and -3%. During pull(and misfire) it was ranging between -7% and -11% on that one bank.

What are engine healthy numbers? Specially during load/rpm, do you know?

PS: All the sparkies had quite a bit carbon on them, but since i recently took over the car, I cant tell for certain it is due to running rich or simply if the previous owner did ALOT of small trips and such.

Just doing some thinking out loud, do correct my logic if it is indeed flawed.
All 10’s appear to run rich, if the fouled sparkies is indeed a symptom of that, and not small repetative driving. So if the sparkies confirm the rich condition, that suggests O2’s are operational.

Now if the fuel rail were leaking, sparkies wouldnt be fouled either, so ruling that out. Leaking fuel injector? Surely a possibility, but all 10 of them? Improbable.

What affects all 10’s somewhat “equally?” Manifold leak? A vacuum leak should cause a lean condition no? So not that.

So, potentially defect MAF? Could indeed cause all 10 to run rich, but why the variance between the banks? Only thing I can think of is, either MAF/Carbon Buildup causes rich condition, whilst Cyl2 has restricted airflow, potentially a broke flap piece jammed in the valve, which then corrupts the readings on the bank? As far as I can tell thats one of the few explianations.

Think I will buy a boroscope and shove it in, see whats what inside. Thoughts?

[kvn]

Solved the issue, but figured I might write incase anyone at some point have similar issues.
I noticed a tiny leak in the fuel regulator on the HPFP, ordered a new one, suspecting this could cause a too high pressure in the rail, and bleed over on the other rail aswell. Replaced the HPFP.

The misfire did not go away, but the rich condition was better. Proceeded to carbon clean the intake ports/valves/plugs, despite it being done recently, due to rich condition possibly accelerating the buildup. Swapped the misfiring injector with a to misfire moved or not.

Just did a testdrive, the misfire was gone, thankfully. I have no idea why tho, so I guess that remains a mystery for the ages. Could be on reinstall, something was sealed properly versus earlier or something. The carbon buildup was pretty minimal, so should be far away from causing misfires. I guess when in doubt, just carbon clean.