motegi

UPDATE 7/29/16: SEE POST #30 FOR THE LATEST IN THIS SAGA


HISTORY

I've had my CPO '13 S8 for a few months and it has developed an issue which has for the past 1 month become much more frequent and severe.

Initially the RPM would dip down occasionally while idling and the engine felt like it was ready to stall. It never stalled out completely but the car would shake for a few seconds until I pressed the accelerator and got the revs up. I tried changing the gasoline provider and have only used Top Tier rated fuel. I even tried a bottle of the Chevron Techron Fuel System cleaner additive with no improvement.

But for the past 1 month it has been having frequent issues with starting. When I press the start/stop button the engine fires up briefly but as quickly as the needle sweeps back down on the tachometer the engine will stall out and stop. The electronics continue to function throughout but the start/stop will not reinitiate the starter unless I shut down the car completely, get out, and wait a few minutes. When it does restart it usually is preceded by the starter motor cranking and cranking for 5-10 seconds before it starts.

I've taken it to the dealer 3 times already in the past month and it just went back today for the 4th time. This latest visit is less than 24 hours since I last picked it up. I live about 50 minutes drive from the dealer so it's become quite a hassle to go out there back and forth so frequently. At this point, I'm asking for your input

Sequence of Events:.

The first dealer visit last month was due to the periodic engine RPM dipping at idle issue. After checking for codes and running some diagnostics they couldn't replicate the problem or find any errors and they told me to pick it up. They advised that I try to capture any future occurrences on video and document when and where it occurred.

Several days later the ignition stall issue developed and after 10 tries I got it running and took it back. They immediately thought it could be due to a low battery in the key fob. They replaced the key battery, kept the car overnight, retested it the next day and said that it was resolved. I drove back out to pick it up.

A few days later it happened again. I took it back and after several days of diagnosis as well as their tech's apparent communications with the engineers at Audi they thought it may have been related to TSB 2030688/13. After notifying me of this they performed a software update for this TSB as indicated. In addition, they tested the air/fuel ratio value blocks and engine misfire values at all cylinders and no abnormal values were found. I picked up my car yesterday at 4 PM and drove home.

At 5:55 PM yesterday (not more than 2 hours after picking it up) I went out to move my car into my garage and it stalled out immediately on engine start once again! I quickly phoned the dealer service department that was set to close at 6 and got the department voicemail. Luckily I have the personal cell phone number for the advisor that I've known there for years and texted him. He got back to me a very short time later and arranged to have a driver bring me an A6 loaner and pick up my car this morning.

So this is where I stand right now. My S8 is far too unreliable to be used as a daily driver because I can never predict when it may or may not start. Unfortunately, my profession (acute care surgery) is not amenable to being delayed even 30 minutes with recurrent car issues as patient's lives can literally hang in the balance. Because of this I normally have a second daily driver (Acura MDX - 100% reliable BTW) but I have loaned it to my parents who totaled theirs last month until they are able to purchase something else so I desperately need to get the S8 fixed.

If anyone here has any ideas at all (even far fetched ones) I'd greatly appreciate your input! I'll relate any of the suggestions to my service advisor who is just as frustrated as I am.

Jack88

Key fob battery? Really? That was never an option for the symptoms you describe. Did they tell you if it was throwing any codes? What's the mileage? Is it doing it only when cold or when hot?

Based on what you describe, it could be a crankshaft position sensor, fuel pump, or any number of other things. Without a list of codes thrown, it's hard to pin it down too much.

motegi

Thanks for the reply.

According to their service techs no codes were generated at all.

The mileage is just under 50K. But it is CPO and I have purchased the additional zero deductible warranty extension on top of this.

In retrospect the ignition stall issues have usually occurred within about 1-2 hours of parking the vehicle outdoors. I'll drive it, park it, and when I come back to start it up 1-2 hours later it stalls. I don't recall it ever happening if I park it in the garage or overnight indoors or out.

But the RPM dropping at idle seems to occur at any time...

I just got off the phone with the service manager and he still thinks it may be related to the A8/S8's "sophisticated immobilizer system" but he says that the only thing that doesn't fit is that all key faults should register a code and there have been none.

I'll ask him about the crankshaft position sensor.

MP4.2+6.0

On a D3 anyway, yes could have been crankshaft position sensor.

In addition, it could be fuel pumps. Any of the rear tank pumps, or the high pressure pumps (HPFP) for the FSI. A guess is it may be the rear tank pumps--two of them if like D3 still (should be). The rear pumps move the fuel up to the front of the car where the HPFPs push pressure way up for the direct injection. I think you typically see codes if it is the HPFPs'--both lean and misfire. Hence why a guess is the rear tank pumps, which may have no codes.

One more check idea you can also do as a DIY, and unrelated to fuel pump idea. You say car stalls if you run it, then park for an hour or two outdoors, then restart. So, if you can replicate that, before the restart, try opening gas cap and see if system is pressurized (likely). Let off pressure. Now try to start. See if any different result. If so, maybe something in the fuel vapor recovery system. Not a common Audi issue, but just going by some of the symptoms you describe--that is parking outside, which I'm guessing means sun/hot this time of year, which could be loading up vapor recovery system.

motegi

Thanks MP4.2. Both are excellent ideas and I'll relate them to my service advisor.

Ravill

Did you take a video of the problem?

Did you show it to the dealer?

Post it here.

Could this be the dreaded coolant extravasation through valves on the ECM? Cars will do all sorts of weird things like this.

The immobilizer doesn't make sense because your car starts.

It is understandable that you will receive no sympathy being a health care professional who can't get to his job because the car "won't start", "again".

ppinto1

The cam position sensor in my '95 90s would only crap out if the engine was warm. It reminded me of your issue.

My '98 A6q had stalling issues that ended up being the mass airflow sensor. Funny thing is, it never threw a code. I didn't realize what it could be until my transmission went into limp mode - and I went down the diagnostic tree in the Bentley manual.

Speaking of which, I miss the Bentley manuals! Apparently, the best manual I was able to get was in the form of a PDF - and it required me to register my VIN. The price was very reasonable, but I feel it's inferior to what I used to rely on.

motegi

No I never got it on video because it is intermittent and I'd basically have to video record every time I hit the "start/stop" to try to catch it happening. When it happens, the stall occurs so quickly that there is not enough time to turn on the phone and hit record.

Can you elaborate the coolant extravasation issue?

I thought the immobilizer reasoning didn't make sense either because the car will actually try to start. Anytime I've tried to start the car with the wrong key in my pocket it won't start at all. However, according to the service manager the A8/S8 is different from other Audi's in that the car will still try to start when it detects "a key" in the viscinity. But as soon as it determines that it is not the "correct key" it will shut off. I'm still somewhat skeptical but that is what I was told. I suppose I could try to sit in the A8 in their showroom and start it with my S8 key in my pocket to see if it behaves the same.

the_duke

https://www.audiworld.com/forums/a8-...rness-2862459/

motegi

Thanks for the link!

I'll ask them about it.

My service advisor just called. He drove the car with the service dept manager and they were able to replicate the problem after driving, parking the car in the sun for 1-2 hours, and attempting to restart.

They said that there are still no error codes being generated.

They are in communication with the Audi Technical assistance engineers again and hope to narrow things down.

Apparently an Audi regional expert will be coming into the dealer this afternoon to look at it as well.