Ltdplus9

I got my Audi back and wanted to share the final diagnosis with everyone although I'm not confident this is a done deal yet. After 3 weeks with the dealer, they believe they have a confirmed fix. All things considered, and assuming it is fixed, I think they really took care of me. I'm not an automotive savvy guy so I'll default to what they told me and wrote up on the ticket. Here are the details;

The invoice description reads as follows;

"Random misfiring at times on cyl 2 & 5. Moved coil & plugs and misfires still present on cyl 2 & 5. Removed supercharger and swapped fuel injectors on cylinder 5 to 4. Misfire followed injector. Replaced cyl 5 injector. Misfire still present on cyl 2. During test drive, misfire on cyl 3. Moved coil to cyl 1 and misfire followed. Replaced cyl 3 ignition coil. Opened TAC case for hard fault misfire on cyl 2. Injector previously replaced. TAC suggested cleaning valves."

That's the write-up. I spoke with the tech that worked the car. He said the valves weren't bad but the TAC asked for pictures. After he sent the pics, the TAC recommended cleaning. The tech mentioned that minor carbon build-up could upset air flow to the point where it creates an unbalance and kicks the ECP. Anyway, they said they drove it multiple days, cold and hot, and the issue seems to be resolved. It's running well now with no issues. Throughout everything, the dealer invested a lot of diagnosing time, and replaced a spark plug, injector, and ignition coil. At the end of the day, they only charged me for cleaning the intake valves - $800. They also gave me a new A6 (3.0) loaner for 3 weeks. If it is indeed fixed, I think they took care of me. If not, I guess I have 12 months of warranty on this work. Are you guys convinced it's fixed??

Nakedhoof

Sounds they did a thorough analysis, and likely identified the problems, and rectified them.

I picked up my car from the dealer this afternoon. On the repair order, it shows that a piston ring was found inside the oil pan. The cause of the failure was a broken piston. I would say most definitely a manufacturing defect. Also, the transmission cooler was leaking, which they also replaced.

OT: I had a Q5 loaner for the past two weeks while they did the work, ordered the parts, and made sure all was working correctly. I can see why people like SUVs, as this was the first time I've driven one. In the end, the thing I liked the most over my A6 was the height of the seats, basically allowing one to step out of the vehicle more easily. Nothing else impressed me over the A6. I'm very pleased to have my car back.

tenspeed

I agree.

It does make me wonder why your engine had both bad injectors and bad coils at the same time. You have new parts, valves cleaned, 12 month warranty and a loaner vehicle for $800. It could have easily been worse.

DanfZX14

I concur with the gentlemen above and given how much effort the dealership put into resolving this problem my gut tells me they will stand behind everything they did and more should the problem occur again.

Ltdplus9

AMEN to that. My initial "emotional" reaction was to take it somewhere quickly and trade it in before my CarFax got tarnished with the issue. But I think I'm gonna stick with it. I still love the damn car.

IknowHuhA6

Glad this was under warranty. I still stand on my soap-box that modern techs just follow instructions sheets with no real clue how to diagnose basic engine dynamics. For the rest of us with no warranty... we're paying for novices to learn and figure out what the problem is. Something they should have been trained for in basic engine management and specialized Audi operation.

Although I admit I didn't even think of carbon buildup being possible culprit but makes sense given our engine's history of this being an issue.

In the end... the heavy carbon buildup in the particular cylinders caused hotter temp buildup and most likely detonation and thus the misfire. But why did the car not show a misfire code at that cylinder?
Cough cough "Planned obsolescence" Cough Cough...

My question to the techs would be....
"Why are those specific cylinders getting higher buildup over others?" Just my curiosity.

Sometimes it's just the design of the manifold, but sometimes it could be bad injectors or bad coils over long term operation causing inadequate burn and carbon build-up. If it's even across engine it could be a failing O2 sensor (aka AFR sensor), but individual cylindrs means coil or injector.
If it's an entire bank it could be our fancy air diverter flaps at each bank.

Glad it got diagnosed and fixed. Great learning thread for the rest of us.
So interesting to learn about how our engines are managed.

Thank you much!

GDI Tech

This is so common out there with most all brands/makes/models of GDI engines. The factory provides so little info to the dealer techs on coking issues and the related symptoms. This is not an Audi only issue and plagues all newer GDI engines. As the intake valve coking progresses (and it starts forming deposits within a few thousand miles from new) the air charge is disrupted. As the coking never forms equally on all intake valves, but much quicker and more severe on those closest to the point of ingestion (differs from models depending on where PCV evacuation vacuum connection is) these cylinders begin to run richer than the rest. The valves furthest from the point of ingestion build far less rapidly will run too lean. Misfires are the symptom, and before that a growing delay or hesitation when accelerating from an idle (throttle response from idle) , and as all cylinders on that bank are samples by that upstream O2, fuel is still commanded equally to each injector so it only progresses further. Just make sure the cleaning is NOT an engine running solvent based and the intake manifold/super charger is removed and a manual cleaning performed as damage occurs from the solvent based cleanings in GDI engines, and only a small portion is ever cleaned. You want the valves to be as clean as new. If not doing so, ONLY run a premium FULL synthetic oil, and never a synthetic blend as some dealers push. The syn blend leaves many times the residue when burnt VS full synthetic.

Always use top tier fuels as the added detergents (all fuels have minimal required detergent additives, top tiers have additional additives) not because it has any impact on the coking, that it does not, but it helps keep injectors clean so the fuel spray pattern is precise. If partially clogged, the pattern is not as fine and droplets form that do not burn correctly contributing to the issue.

Look at having a system like in the "Intake Valve coking" thread as that will prevent up to 90% of these formations.

I highly doubt there was a coil or injector issue. They were just doing as trained, swap parts. The misfires will be random in nature when the coking becomes severe enough, and visually it may not have looked bad, but any buildup has a substantial impact on the intake air charge flow around and past the valves.

Glad you had a happy ending!! Most either are not aware of this at all (including dealer techs), or disbelieve the auto industry has taken this step of new issues and care GDI engine equipped vehicles need. As the degradation is gradual, most never notice until they trade, so you stuck to your guns even w/out being a mechanic until they correctly identified and dealt with your issues.

krboland

Same thing regarding the EPC light and terrific shuttering and almost stopped in the middle of the DC Beltway. Right at 55k miles

My 2012 Audi A6 did the same thing regarding the EPC light and terrific shuttering and almost stopped in the middle of the DC Beltway. I just went over 55k miles, and had my last “service” about 6 weeks ago (I did one service early so all my services are done now…I have been very careful with the car) as well as a computer update and all of the various recall items taken care. I also had the AUDI Service Rep update my Service Book with the stamps for all my services. They offered another service for close to some two thousand dollars in the future, but I told them I would consider the offer.
So, at this point, I too was waiting for the “other shoe” to drop now that my services are over and it did right on cue!
Not sure what to do with the ECP light and the shudder/stopping issue as it is quite the hazard if you are doing 75 mph and all of a sudden your car shudders violently and comes to a stop in the highway. I do not wish to be forced to spend an exuberant amount of money to get the car back into a safe driving condition.

It is a 2012 AUDI A6 with 55k and the “prestige Package” and Cold Weather package (nice looking and comfortable car….when it is running). I still owe $25,000.00 on the car, and am counting the days to when I can go back to driving a Nissan (they never caused me problems until after 150k miles).

But for now, I am stuck with this car.

Any suggestions?

krboland

When my 2012 Audi A6 did the same at 55k just after last service and I was driving about 75 mph on the DC Beltway, I coasted to the shoulder, turned-off the car, then turned it back on again and finished my drive to work (10 miles) with no other problem.

During my 55k service, they updated the softwear and did all the required recall items.

Could it have something to do with the updates?

I no longer want this auto (nothing but issues), but owe 25k so I am sort of stuck with it.

BOPOH

Dont worry, minor hiccups are normal - either 1) coils are bad or plugs, dealer where I bought my car had EPC light so they replaced spark plug and coil. Plug was the cheapest piece of junk you can find, it kept giving me issues until I replaced all spark plugs. 2) If it is indeed intake valve carbon buildup, cleaning is super easy and cheap diy. I did it along with other maintenance and it's running fine - here is how i did it CLICK HERE