SENS8

Well, on the one hand why would Audi seek to conceal anything when they're bearing all the cost under warranty, and more to the point: what do I / we care (as to whether you suspect the diagnosis) when what we DO know is that the car has since run so far 113k miles perfectly (the only thing replaced has been a failing headlight bulb and an armrest clip)--?

(I am myself prepared to believe that the starter may have its own grounding circuit, and that ignition grounding under load and vibration is evidently a separate phenomenon).

In any event, if CARBON accumulations (subject of this thread) were to have been my real problem (and that is how the misfiring error codes were first interpreted), this "problem" has resulted in my engine running if anything continually better, and so far as I can extrapolate, literally indefinitely.

mishar

I totally agree with you - Audi wouldn't conceal something like that. May be something like burning oil in brand new 2.0T, or carbon deposits in otherwise perfectly good engine, but not something like engine grounding. But dealership, on the other hand, or proud overpaid mechanic, might be tempted to conceal ignorance. Especially if it caused certain expenses.

I am happy that your engine is running well. I would just be happier if we learn something from this, but I doubt that grounding is our lesson.

You may be right about SOME grounding. I would like to know which one because it might help somebody in the future. Engine is big mass of interconnected metal, including starter. If starter is grounded all of it is.

I am very happy to hear that you didn't have any problems. Actually it is very rear to hear it on forums like this for the simple reason that people write when they have problem, not to tell others that all is fine (like we would if we are writing to our mothers )

s4master1

Have to agree with mishar on this one. just because they tell you it was lack of proper ground doesn't mean it was your problem.
Dealers and most businesses will tell customers any vague thing relating it to the cause or solution assuming the customer has no clue anyway, as in your case customer don't care as longest the car runs well.
I can bet you it was the catalytic on the driver's side the one that failed as is the most common to fail first, I would need the entire page to describe the reason why this happens but would be a waste of time as you stated the car runs better.
What if I tell you the computer was reflashed with a different set of driving maps and that is the reason you feel better acceleration than before without affecting mpgs.
the injectors are controlled by the ecm thru the ground side not the positive side, they handle very low voltage and open by milliseconds, so fast that a bad ground would not affect them at all, ignition coils are also grounded thru a secondary circuit and not much to do with the engine/transmission ground at all, all the other input/output units as sensors and actuators use so little ground that even if the engine was not grounded to the chassis the engine and transmission mass is so big that they would work perfectly.
engines specially loose some voltage due to temperature but is very insignificant to even be a factor on the air/fuel mixture.
on the carbon build up most people would never notice it until after it has been removed and compare the change in performance, all FSI engines have this issue from 2.0 to 5.2,
For those who rave about cleaning solvents and procedures I suggest to be very careful using abrasive solvents or just avoid them altogether
try reading about thermodynamics of materials and specifically alloy properties on these engines, some people still compared this engines to old cast iron block engines.

SENS8

(Whatever the relevance) it was my passenger-side catalytic converter that denotated with the unignited fuel mixture. And it seems to me that spark plugs still require megavolts rather than millivolts, on any engine. BUT as a layman I do appreciate being educated by those here with actual engineering knowledge.

Are there any forum lurkers with even more than 113k miles on their V10, so as to give me peace of mind, in turn--?