I’m back.....and misfires

A6 All/ S6 All
#25

I just randomly decided to check these forums finding your thread. Very interesting as my car is fucked right now as well with similar symptoms. I have an 2008 S5 which I replaced the battery with some O’Reily battery in Sept '18 ignorant to the need to program/discharge the battery to the car.

I have had intermittent MMI power surges, especially under full throttle, happened about 5 times since I installed the battery. However, right now my car feels as if its in full limp mode with anything beyond 1/4 throttle depression. Shop discovered HPFPs are not functioning electronically (they can manually turn them on, test them through VCDS, and they make pressure upon ignition, but after that nothing). Also at the same time pumps failed, my right front head light ballast was fried. We have replaced HPFPs, high pressure sensor, discharged and programmed battery, checked SAI, checked fuel for water, checked gas lines for pinches/kinks, checked wire harnesses, LPFPs…everything. We are not at replacing the ECM reprogramming it, and then reflashing the APR tune.

Been in the shop for 5 weeks now…I may ask them to do the battery to OEM next ???

#26

Replaced my aftermarket battery for a new OEM and I still have same problem. Onto the the ECM now

#27

The battery is a issue for lots of people and to be honest its something to make sure your on top of but in the case where the cars have more than one code espically for fueling you want to go down the path of checking LTFT and all other areas.

#28

I’m going to order a vagcom and go from there, I know I know I should already have one. What areas should I check once I get it in?

#29

Well just to get everyone up to speed. Car is still misfiring, I’m on my second mechanic now, his son also owns a s6 and he has worked on it so maybe that will help.

However, I met a Land Rover service advisor last night and we were talking. I seemed to have developed an intermittent exhaust sounding rattle on the left side, not all the time but occasionally maybe once a week or less. He seems to think that one of the cats ceramics is damaged which is causing me to have such a shitty startup routine. He has an Audi/VW tech that’s working for him now so he says to bring him to diagnose for free, and he has some expert exhaust folks that can fix if need be. I told him it’s an engine drop to replace the cats and he acknowledged that so we will see. So it seems i have my third option now.

#30

Hopefully it’s not cats. Dropped my car off this morning and forgot all about mentioning my cold start misfires lol. Probably won’t get the car back today anyway, but pray for us S6ers

#31

Headed to third shop tomorrow, wish me luck!

#32

oh man… This is a great example of just how special these cars are and how few really know about them.

Are you getting any codes or stored codes. Usually the cats are something you get a code for. What are your fuel trims? Check fuel trims they are a good first line is helping tell you if you have a leak or not.

Next time you start your car pull off the plugs from the MAF sensors. If the car starts up better and isn’t having misfires as bad that would tell you something as well.

#33

Missed this post. Will check those items out. I had a hunch it might be MAF related awhile ago. This seems like an endless witch hunt…they ruled the cats out somehow and said the rattle I heard was the exhaust hitting up against something so I guesss that’s goods news.

So far the third shop has said that the previous shop has been pretty careless with their work . Their diagnosis so far is:

  1. Bad Vac leak under intake manifold and potentially elsewhere including gaskets to the IM itself.
  2. The throttle body gasket that the previous shop replaced is leaking as they think it’s the wrong gasket
  3. They claim the air intake tube to the throttle body is warped causing turbulence as well.
  4. They claim both banks are running rich which is interesting because you would think if you had a vac leak you would be running lean. Not sure if that’s actually triggering a code, or they are just looking at fueling. If only looking at fuel trims that could be misleading cause the tune could be causing me to run rich.

I spoke with Jimmy and we don’t honestly think that these leaks would be causing these amount of misfires, but I guess it may be possible. I have misfire on 1-4-6-7-9

That’s all I know so far, this is an Audi tech at a Land Rover dealership but he has all his equipment. I know the SA and they are diagnosing for free, hope to know more Monday.

#34

Well that would be good news if all of this is due to bad gaskets and vac leaks. Those things sound like they are relatively cheap to fix I guess. Maybe the car is just trying to catch up with the leaks to balance things out and leading to misfires.

#35

Hi!

I’m new to this forum and to the S6es.
I bought my first S6 in mid May, this is my third Audi so I know my way around them.

When we picked up our S6 it has a couple of fault codes.
Misfire on a couple of cylinders, system to lean on both banks and so on.
When it was idle I removed the dual hose “box” going in to the PCV, the already rough idle became more rough.
When I then blocked the hole to the PCV with my hand, the rough idle completely stopped! I could place a cup of coffee on the intake manifold, with no spill. It was totally stable and a completely different engine!

So I did, as I’ve done on our previous A3, a PCV delete. The valve breather that was going in to the PCV is now breathing freely to the atmosphere through a 22mm hose in each side.
Our A3 did 160.000 km with such a set up (total 335.000km) and the S6 has done 2.000km now with this setup.
Still no misfires and no faults whatsoever. Engine is still rock solid on idle and it is as new!

My suggestion is to give this a try. No tools required!
Just pop the The dual pipe going in to the PCV and block the PCV with your hand. Be aware of the strong vacuum!

#36

Can you post a pic?

#37

Do you do much sitting in traffic with the windows open? I would think you would smell burnt oil in the cabin.

#38

My pcv was replaced a few months ago.

#39

Sure.
Remove the red circle and block with your hand at the green arrow.

https://d2aztkdj0ezvrk.cloudfront.net/items/3C3r1C2E0z3O45281T09/Skærmbillede%202019-06-23%20kl.%2009.16.46.png

No, windows is normally closed, I normally just use the sunroof.
But I did try yesterday and I didn’t notice any smells. My A3 was a TDI and the smells there was horrible.

Then it might not be the PCV, but it wouldn’t hurt to try it out.
Just block the end pipe at the green arrow with your hand and get someone else to start the car see if it makes a difference. Wouldn’t hurt.

#40

That is the oil separator and the PCV unit. Its a terrible idea to just leave it open. Its the PCV that system keeps the crank case pressure down and helps keep carbon more at bay.

The idea on opening the PCV system for testing just to try is a great idea. To actually have that as a long term solution is a bit absent minded.

On some cars without the oil separator maybe its not as impactful but since the V10 has a long history of blowing out gaskets venting to atmosphere wouldn’t be the greatest idea. Also remember that on the closed ring gaps you need to have vac pulled out to keep the rings sealed. So for multiple reasons it would be a terrible idea to not have the system hooked up.

Lastly if you know that unhooking and blocking off the oil separator and PCV unit stops any misfires why wouldn’t you just replace the unit. In theory you basically just proved its bad.

Kimovitzh welcome to the forum. Thanks for the post and suggestion… Maybe try seeing how much oil of any comes out of the PCV tubes since they’re not hooked into anything… Also keep us posted many in the past that had issues with holes in their PCV units or hose ended up getting fuel trim codes. It would be interesting to find out what and why.

#41

With that in mind wouldn’t negative pressure in the crankcase then encourage blow-by?
Also, 2 x 22mm pipes ensure that there is no pressure.

Can you elaborate what part you mean when you say “the closed ring gaps”, what part do you refer to?

A working PCV-system is still letting a lot of oil (relatively) in to the intake manifold, and then there is the longlivity of the PCV in it self.
The previous owner had it replaced a year ago at Audi in germany and already it is broken again. When I removed the manifold to clean the valves, 250-300ml of oil was sitting in the manifold, only way it can get there is from the PCV (also the water cooled pipe from the PCV to the manifold was full of it).

As I said before, my A3 with free venting crank had no problems at 335.000km, that’s 160.000km, over 7 years, with no mechanical failure and no engine parts replaced (The EGR was deleted as well).
I’ve seen multiple cars run fine for years with a free venting crank, from 3-cylinder to V8’s, and not just old v8’s ;).

If you read around the internet, and that’s a bad start to begin with, many people has the same concerns as you.
And equally the other way around. And I get that people are concerned.

Thanks for the welcoming!
I’ll be the ignorant guinea pig with this controversial fix, maybe start my own topic with interval reports, huh? :slight_smile:

#42

Well to put it simply. Your venting to atmosphere so only when pressure in the crank case is enough do you see any venting.

The PCV system is self is SUCKING air out of the crank case. BIG DIFFERENCE and even bigger results.

If you have too much negative pressure in the crank case yes that could encourage blow by but since the vac is equal to the intake of the air that is negated.

If there is a good amount of oil in the intake then by default the oil separator isn’t working efficiently and thus the PCV system. Also if you unplugged the PCV system and resolved your issues you just proved it was broken in the first place. So if the part was replaced a week ago or a year ago its not working properly.

This gets me off on a tangent on shops getting cheap replacement parts and not the better made OEM or close to oem units.

And sure you can unplug lots of stuff and have lots of stuff not hooked up but that doesn’t make it right or the correct way to do things. It also doesn’t mean you’re not causing other issues.

With that being said and that is just the word of reason and caution. HELL if your getting workable results great. Just report all the good and bad because if you were getting 300ml of oil in the intake with a non working oil separator your still going to get that oil its just going to be coming out the hose or other pipes you have hooked up.

As you said. The internet is full of BS bullshitters and just endless shit when you read some forums. I would strongly suggest you start a thread on this. I think its a great idea. The only thing I would say is don’t be that guy… and by that I mean if this ends up being the worst idea ever and works like shit… just say so. SHOW ALL THE GOOD AND>>> THE BAD…

This forum is small but we have been lucky. We have kicked out or ran out all of the ultra bullshitters. Its amazing how full of it some guys were. So if its good info or good info on something bad. Please post it.

The FVC thread.
#43

I’d still love to replace the PCV with something like a catch can if it were possible…

#44

We have a kit available but there’s a new version to be released soon so you may want to wait a few weeks.

www.savicorp.com