C6 S6 misfire

A6 All/ S6 All
#1

One if the members (V8A6) recommended in post here as opposed to audizine, so here I am!

I’ve searched to no avail on this issue; as far as I can tell, no one else is experiencing it/has experienced it.

Related or unrelated data:

  • 5.2L V10, muffler delete, no other mods, 2008 Audi S6 (pre-facelift), 76,000 miles
  • I just had the carbon cleaning done on the intake valves. The car was misfiring at 3-4k RPM’s consistently on one cylinder. Replaced the injector on that cylinder and all was fine.
  • The car, when below half tank of gas, acts noticeably different, especially during warmup (a lot rougher the lower the tank is). I don’t think this is my imagination.
  • Fuel gauge seems to be off but hard to say for sure. When I fill the car up, it stays “full” for quite a few miles. As the tank depletes, it eventually starts to line up with where I think it should be. Could just be an Audi thing (first Audi I’ve owned), or my imagination, or mean nothing at all.
  • My ABS module needs to be replaced (ABS/ESP/TCS lights are on, parking brake malfunction… the works. Audi says I need a new ABS module and the internet seems to agree)
  • A year or so ago, the engine threw a code for low fuel rail pressure that never came back, and only once.
  • The car will have a very light “smoke” coming from the driver side of the engine bay occasionally. This ONLY happens when driven hard, generally when corners are involved. I drove from Seattle to Portland (200+ miles) and the smoke didn’t appear, but it does after hitting a corner quick, but not always. The smell smells like a burnt rubber but I can’t tell. The tires look fine.

Take this info with a grain of salt. I’m a computer science guy, not a car guy. I have more knowledge than your average guy but not near enough.

The problem:

ECU has thrown two misfires for P0300 (random cylinders) as well as 7, 8, and twice on 10. I’ve revved it high and hard in a straight line, even after clearing the codes, with no problems. These codes, however, were all thrown while accelerating hard around a corner from a stop. Am I just being an idiot doing this? Or is there something I need to address? I’m guessing fuel system but can’t be sure. Also thought it could be motor mounts. Again, not sure. The engine doesn’t give too much of a rumble but you can definitely feel it in the cockpit. Of course, it is a V10, so I figure this is normal.

The car had an odd idle feeling this morning after clearing the codes. It would get very quite and then bounce back to normal volume. The RPM’s would range from 630~680 at idle while warming up. The problem seemed to dissipate after the car was warm and had been driven a few miles.

Also wouldn’t mind recommendations on the ABS module. Would like to get away with getting it done RIGHT but not spending $2300. I will do so if necessary though.

Thank you all!
Nate

#2

Nate your in the right place. All the technical guys are here. The guys here just don’t know about cars they work on them so your going to get real help here.

Let’s tackle this one at a time.

The abs module. Try contacting module masters. I don’t know if they do units that new but it’s worth a check. They are known for fixing these things but it’s been a while since I’ve seen anything on them. Try that and report back if you can.

the smoking from the one side would probably just be a leaky valve cover gasket. And a old pcv system. Under hard acceleration your pcv system is supposed to pull built up pressure in the valve cover and crank case area out. From time to time too much pressure can build and you can get oil pushing past the gasket.

The fuel pressure code is something you want to keep an eye on. The possible link to the amount of fuel and feel of the car running bad is kinda hard to link together. But you might want to replace your fuel filter if you haven’t at this point.

The cold start misfires are not uncommon if you have carbon build up or a clogged PCV system. A
so check your coil packs and plugs when where they replaced. When getting misfires at high rpm usually the list goes check
Fuel filter
Plugs
Packs

If you got more questions toss em at us also please make sure to check in when you find out more information

#3

Sounds great, I’ll start on everything asap and update as I go.

Have you (or anyone) had experience removing the ABS module without bleeding the brake lines? I’ve seen examples where the hard lines have enough give to allow the removal of the module (therefore rendering the vehicle still operational even while having the module fixed, which is very desirable), but can this run me into big issues?

#4

Welcome to AudiRevolution !!!

justin was one of the guys that I was referring to, when I mentioned that we have the top level Techs over here. He is very generous with his time, helping out AR members. So, you’re in good hands.

#5

That’s great to hear. If any of your contributors would like to receive help with PC’s at all (any Windows machines, sorry, no Mac or iOS devices) in any way, I’m more than happy to assist. I feel that’s only fair if I’m asking for their time.

Thanks again.

#6

Wanted to see if you had any updates for us.

It’s good to know we have a goto guy for pc help. I thunk one of the best ways you can give back is to help bring more good members here. One of the biggest problems is the v10 guys can get scattered all over the net and when all the technical guys are here but the guys who need help don’t know where to go that starts big issues. Helping others find the help here is a big step.

#7

Great point Justin. The more v10 guys we have over hear, the stronger the knowledge base and community grows. If you see another v10 S6 guy looking for help or info on performance mods, invite him over.

Just an FYI, the word AudiRevolution is blocked on Audizine, even in PMs. So, if you mention AR, type it like this…

Audi Revolution .NET

And for a good laugh, check out the advice illumiNatev10 was given on AZ before I told him about AudiRevolution

http://www.audizine.com/forum/showthread.php/656396-C6-S6-Misfires

Too funny

#8

Karma for you v8a6. With advice like that no wonder they block audirevolution.net over there. Good for you to help get people help and helping get them here. Wow what a lol fest.

#9

Weird, I figured the fact that I’m on an Audi Forum for, well, DIY’ers would somewhat indicate that I’m ok with DIY. I wouldn’t have purchased a performance vehicle from a German luxury brand if I wasn’t willing to get my hands dirty, or pay someone way too much money to do it for me (not too keen on the latter).

lol, just goes to show man… Pretty standard. Happens in the computer world too when people take their shit to Best Buy’s “Geek Squad” lol.

Anyways, I haven’t had time to look into it yet unfortunately. If you have time, would you mind giving more information on that PCV hypothesis? For instance, how I would verify it, where it’s located (roughly) and what it looks like/does? I hate to ask for more of your time, but I’m pretty stranded as I’m really just starting to dig into cars (mostly have just been watching youtube videos on engineering to figure it out from the ground up).

And what do you think about that gentlemen’s recommendation of a compression test? How is that achieved, cost associated, etc.?

Also, new info:
Took care in for oil change, they said the thermostat is beginning to form a small leak. They recommend replacing it before long but shouldn’t be any immediate danger, though that can change I’m sure. I noticed a “popping” sound coming from the engine (I can hear it through the exhaust pipes) after I turn it off. Sounds like the metal-cooling-down sound most cars emit, but it seems louder than usual. Maybe something to do with the thermostat? Who knows.

Another curve ball… I had to replace the coolant reservoir a year or so back (pin-hole leak), had Audi do that (was relatively cheap), but ever since then I noticed a strangeness to the pressure of the coolant loop. It sounds a bit like my liquid cooled gaming rig did when it was shutting down and pulling through air pockets (Pressurized liquid flowing through a loop with an air pocket?) I built that machine, so I figured that out eventually, but I’m out of my element here.

Closing statement for this post:
I know it probably seems like I’m just some moron asking “how do I fix my car for cheap?” but this isn’t what this is about. I’ve had a passion for things that resemble the power of the gods (e.g. careening through space and time at the movement of your foot) for as long as I remember, and German automobile engineering is the next thing on my list to learn in-depth, through and through, not just surface scratching. This is the first of many luxury Euros I’ll be owning. I appreciate any help I get along the way, and thank you guys a ton for the help you’ve provided thus far.

#10

http://www.ecstuning.com/Audi-C6_S6--V10_5.2L/Engine/Emissions/PCV/

I will defer to Justin for more in depth explanation of pcv system function but these parts will be found most likely on and around your valve covers area usually toward rear of the engine. When you do locate them on your engine check the hose isnt brittle or cracked, see if all the connections are good. Careful as just doing this can break already brittle connectors. If you can safely remove it, inspect to see its (hose and valve) not clogged. Yes, I did this on my old b5 s4 diy. I know its a different car but the concept and function is same. Audis (maybe other makes) are not known for the best pcv systems. Faulty or clogged systems allow too much pressure to build in the valve covers and cause leaky seals and gaskets. Happy hunting. Shouldnt be too hard to locate the parts on your engine though.

#11

illumiNateV10 don’t for a second think your asking for too much help. That’s why we are all here and not on the other forums. We are all here to help. Even if that means a step by step post and walk through. I just did something similar on the S4 section with a guy pulling his motor for a timing job. So really don’t think not asking questions is better. Always ask questions.

Let’s start with two things.
1 get a vag-com it will help us help you and with that as a tool help you help yourself.

And yes get a compression test.

#12

I might getting completely off base but could this be a bad or improperly installed injector? When I replaced them they did tighten all the way and obviously when running hit it would blow off a little smoke and smiled gasy, thank god I fixed thst quick! My csr also ran extra lumpy at idle with worn injector. Just a thought.

#13

Its quite easy to check if the PCV valve or oil separator is faulty; simply try and removed the oil filler cap or dip stick with the engine running and it will be very difficult.

Heres a link to my experience - http://forum.rs246.com/viewtopic.php?f=44&t=111182

and an example on youtube - https://www.youtube.com/watch?v=cLSEgGtMatk

If however its the check valve within the vent pipe im afraid its a manifold off job.

#14

Regardless of what you decide to do. You should seriously look at getting a vag-com

#15

Are all Vag Com’s created equally or should I look for a specific one? For example, would this have access to all of the codes the car is capable of giving me?

Thank you guys, it means a lot to know I have a place I can get my questions answered.

http://www.amazon.com/gp/aw/d/B005I7JAX8/ref=mp_s_a_1_2?qid=1435809226&sr=8-2&pi=AC_SX200_QL40&keywords=vag+com&dpPl=1&dpID=31QU4iIKr1L&ref=plSrch

#16

No, they are not and that one likely will only yield general fault codes. Just get Ross tech registered vagcom. Others may have options that worked well for them, but going through the real deal site is the better option for full functionality.

Opt for the torque app and a cheapy blue tooth obd2 connection if you just want a scan tool.

Although reading that units description it sure seems it may work, but also a hint of too good to be true to me considering a real vagcom registered cable from ross tech is a few hundred $ or more.

#17

I want a tool that supply me with all of the data necessary. I’m assuming stuff like this
http://www.amazon.com/gp/aw/d/B00WSB46D6/ref=mp_s_a_1_23?qid=1435997126&sr=8-23&pi=AC_SX110_SY165_QL70&keywords=vag+com+audi

Won’t work? I would assume it would because a PC would certainly be able to receive all of the data, I just need to make sure the software will parse it and it’ll function the way we need it to. I didn’t find anything on Amazon from Ross Tech, and most of the scanner seem to range 60-150. I want as much data as I can get my hands on so I can start isolating engine problems and fixing them (hopefully)

#18

Ya, you wont find ross tech on amazon i dont think. Just go to ross tech sight for real registered cable with suppirt and full function vagcom. Unless you want to try and figure out the other options and how to get them to provide full functionality.

#19

Exactly your going to want to use a tool that has lots of options and that others can help you with if you get stuck. Getting a cheap cable or trying to save money might be an issue if people need more information then what the cable you get can offer. Also i and others know there way around the vagcom software and will be able to help you not only find things in the software but whats codes to enter to activate options if you need to

#20

I looked at the options, and it looks like this is my best bet:

http://store.ross-tech.com/shop/VCHUC.html

$350 is kinda rough, but it’ll do everything I’ll ever need, correct? I’m not seeing a cheaper option anywhere. The cheaper cables all looked like they were for older models.

Thanks