So hopefully this forum is a little more helpful the one that will remain nameless. I have a 2006 S4 with 87,000 miles on it and its all stock. The original problem was no power and I was having codes for P0171 Lean on bank 1, and P 0305, 0307, 0308 Misfires in 5, 7, and 8, So I replaced all the plugs air filter. Still had no power and code P0171 for bank 1 but no misfire codes. so I swapped Ing coils for bank 1 to bank 2 to see if it would follow and it didn’t. So I move on to replacing the PCV valve, do a carbon clean, swap inj. from bank 1 to 2, and install intake spacers. While the Intake was off I noticed the valley pan was leaking so I replaced the gasket as well. After getting all that done I do not have any P0171 code but now have a P0431 Bank 2 cat not operating with in threshold. and when I accelerate fast it builds up the speed slowly and makes this sound I have a hard time explaining. Checked for an exhaust leak and only really saw one at the slip flange between the main cat and muffler on bank 2 side but it seems really small if it actually is a leak( just see the black carbon build up) was going to pull the down pipes off and check the cats and hollowing out the pre cats but if anyone has the trick and what tools work the best for this id greatly appreciate a how to. Anyways I thought maybe my mass air flow sensor was bad to I disconnected it to see if the car would get its power back and it didn’t. So I rechecked my vacuum lines and found one vacuum line broke that went to a silverish regulator behind the oil filter housing (there is one on the other side as well) I fixed it and now I don’t get any codes but the power loss is still there. Im at a loss right now any help would be awesome I miss driving my car. Oh and I don’t know if this maters but when revving the eng. it doesn’t make the sound only under load.
sorry it does make the sound under load. and if I go easy I can get up to 65mph no problem.
Sounds like you probably have a clogged cat.
That’s what I’m thinking too. But I’m struggling on how to take the down pipes off… if I take out the o2 sensors It should help with my flow and I should see some increase in power right? That way I know it’s the cat clogged. I have a video of the sound but it won’t let me post it…
[url=http://audirevolution.net/play.php?vid=188][img]http
Welcome to the better forum. Most of the tech smart guys have come over here. We love to see new members come over here loooking for help so let us know what we can do to help.
First off. Even if you were to never want to do any performance mods to the car I would suggest removal of the Pre cats. This causes all kinds of issues when it comes to the motor health. what euro said sounds very correct you have a cat issue
How to get the dps off we can get to that one in a second.
Pulling your 02 out wont help much. So I would leave that one alone and just concentrate on getting the dps off and the cats out.
I thought I did a write up on how to remove the cats and dps. Let me look and ill come back and post again
Thank you. I’m not a expert mechanic by any means but I do love working on my own cars. Just need help from time to time… haha. Being ne to Audi’s I’m still working on understanding the engines. And I agree the pre cats need to go. So any help on how to tackle this would be greatly appreciated.
Any luck on finding that info?
We are all here to help. and we are happy to do so.
Is your car a manual or auto that plays a big part in getting the dps out. I thought I had posted a DIY on getting the dps out but i cant find it.
It’s a manual. And no problem if you can’t find it… if you can think of anything that makes it easier to take off or any special tools that you used… and it’s strange I’m not getting the error code for my cats anymore but now getting g ap0171 to lean code on bank one and it’s misfiring code once for cylinder number 3 5, and 7… i dont have a vagcom but do have a obd2 code logger from a parts store… what kind of values am I looking for? I don’t always got misfire codes but I feel like it is missing.