Please, help me find the issiue - shaking and misfiring

[smolam]

Hello Guys.

I have a problem with my C5 RS6. Resently, I had transmission converter issue so I needed to get the engine out.I decided to make some additional service. On engine side, besides removing leaks I changed knock sensors (broken connectors) oxygen sensors, sparkplugs, temperature (coolant and air) sensors, both turbos (rebuild) plus new timing set.
After first run I had some issues with injectors so I serviced them in authorized BOSCH service and put new fuel pressure regulator.
Now something weird is happening. When engine is cold, works great but then it start shaking and misfiring.
When stops on traffic light is ok but the longer it stands the more shaking. In logs, lmabda correction on bank 2 rising to -25%
Checked intake and it is tight.

I made some logs form basic group. Please take a look because for me, they looks weird, but I am not a specialist.

https://vaglogs.com/log/001-090-003-ddd ... 246b2b8947
https://vaglogs.com/log/001-022-003-416 ... fd22942513

Any suggestion where to look or what kind of logs to make?

[Shoppinit]

You need to log each MAF individually. The total looks a little low when you are full throttle.

The lambda values for bank 2 are all over the place. It could be a vac leak, or possibly a leak in the exhaust pre-lambda sensor. This can happen when an SAI combiner valve fails. Or maybe you've got a bad lambda sensors.

First thing I would do is double and triple check that the airbox is seated properly. It is very common that it isn't installed properly and you get an air leak.

It could be a bad coil pack. I would swap all the bank 1 coilpacks with bank 2 ones to see if that makes a difference.

Log groups:
- 002, 032 and 11
- 002, 015, 016

That'll do for now. My money is on a vac leak, but I reserve the right to change my mind when I see better logs.

Also, do you have any fault codes?

[smolam]

I put 4x Bosch 0 258 010 073 sensors which should be ok for this car.
Intake checked without the air box, and also, both MAF-s sealing are new.
I will check the air box and make new logs.

The code I had was "P1129 - Bank 2 (Mult): System too Rich" and misfires

[Shoppinit]

OK. New lambda sensors, that's good. That eliminates those. Doesn't eliminate faulty combiner valve, though, or another exhaust leak.

If it's running rich then it could be vac leak, coil pack. It doesn't have to be leaking from around the MAFs. Lots of other places it could be leaking.

Since you say you are getting misfires, there's no point logging 015 and 016. Let's see what the EGT are doing instead. Group 112. Also group 047 to see what the lambda sensor is doing.

You could check for a boost leak, but I would not expect this to manifest problems on only one bank.

[smolam]

I checked the air box (with endoscope camera) and it looks fine.
Made a short log during the road form my job.

https://vaglogs.com/log/002-032-011-354 ... 4125397dcd

Here are the error codes form last trip.

dtc.PNG (11.35 KiB) Viewed 1226 times

I haven't this issue before the service, so I think that there is small chance that coils are damage.
I checked intake by sealing the place where MAF are mounted and make a pressure with compressor. There were leaks from intercoolers but they have been fixed and now there are no more leaks. But again, before service this was not an issue.

MAF-s don’t work even, I noticed this also but have no idea why and, at the end, the air is combine together before intake mianfold.

What is the best way to check vacum?
Could knock sensor caused such issue?

[Shoppinit]

MAFs look nicely balanced.

I see you must have cleared the error codes before doing that run, so that reset your trim values (032). I can see that bank 2 mixture is being made more lean until you get a misfire and fault code.

I think it’s a fuelling issue. So coil pack or bad injector or plug.

It’s not a knock sensor. That wouldn’t cause a fuelling issue.

Could be EGT or lambda sensor.

Could still be exhaust leak / combiner valve.

[smolam]

During first run after service I noticed this issue. My first idea was that injectors stuck and passes too much fuel. I sent all injectors to BOSCH service. They have cleaned and tested all injectors. They are (after service) mounted in different order. Because issue stays the same, injectors need to be fine.

EGT sensor shows similar temps. I will make log.

How can I check combiner valve?

[Shoppinit]

What about the coil packs? Swap them all to Bank 1 and see if the problem moves.

[smolam]

Hello,
I swapped coils pack between banks, here are the logs but I have not feel any difference.

https://vaglogs.com/log/001-032-112-4e1 ... f80d30392b

I have been thinking, what can I messed up and found two things.
I could swap EGT sensors sides and mix oxygen sensors connections.
I have change all oxygen sensors and zipped all wires together. I need to find a way to check its order :/
Yesterday I made one more thing, switch connections between oxygen sensor 1 bank 1 and sensor 1 bank 2.
In my opinion was better. Here I the log.

https://vaglogs.com/log/002-112-032-552 ... 93a95e6235

There is also, small chance that one of oxygen sensor is broken from factory. Don’t know how to check it
I have old sensor, what could happened if I connect it for sensor 1 on bank 2 and left it under bonnet. Will this tell us something?