Multiple Cylinder Misfire - No CEL

A6 All/ S6 All
#1

Hello. I have a 2007 S6 C6 with 107k. I am new to the VAG world and I have spent the last year learning and sorting out the many issues it had. I’ve mostly enjoyed the challenge, but there’s one issue I haven’t resolved yet and I’m hoping you can help:
As the title states, I have a misfire only under medium to heavy load. It doesn’t throw a CEL, but it can definitely be felt. The car idles perfectly and is smooth with partial throttle. I have logged the misfires with Vagcom while driving and currently the misfires are in 1,2,3,7 & 9. Cylinder 2 is the worst. The others are very slight. I have replaced all the coil packs and plugs. The plugs looked like they were running pretty lean. I ensured no oil was in plug well with minimal change. I ran 2 tanks of fuel with moly injector cleaner which did make a noticeable improvement. I am also running ethanol free fuel which interestingly helped too. I’ve also done a smoke test on the PCV system and replaced the PCV valve assembly. I did find an old DTC code that may be related and I added it below. At this point I’m thinking the injectors may be dirty, but I’m wondering if there is another vagcom test I could run to confirm this? Does this sound like injectors to you? I’m wondering if there is a sure fire test to confirm before I tear into the injectors?
Thank you very much!
230121_ScanLog.pdf (124.2 KB)
Saturday,19,February,2022,17:29:38:25692
VCDS – Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 21.9.0.2 (x64) HEX-V2 CB: 0.4555.4
Data version: 20210903 DS330.0

VIN: WAUGN94F37N089902 License Plate:

VCDS Release 21.9.0: SRI Reset
Control Module Part Number: 4F0 910 930 C Labels: 4F0-910-xxx-17.lbl
Component:KOMBIINSTR. M73 H18 0120, Coding:2129268
Operation: Please select an operation

Channel Description Unit Current val. New val.
02 Service Reminder Status 1 —
40 Mileage since Service miles x100 101 —
41 Time since Service Days 380 —
42 Min Mileage to Service miles x100 100 —
43 Max Mileage to Service miles x100 100 —
44 Max Time to Service Days 365 —
45 Oil Quality 1 —
47 Soot Quantity km x100 0 —
48 Thermal Load km x100 47 —
49 Min Time to Service Days 365 —

Saturday,19,February,2022,17:33:00:25692
VCDS – Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 21.9.0.2 (x64) HEX-V2 CB: 0.4555.4
Data version: 20210903 DS330.0

VIN: WAUGN94F37N089902 License Plate:

            Address 65: Tire Pressure       Labels: 4F0-910-273-BA.lbl

Control Module Part Number: 4F0 910 273 B HW: 4F0 907 273 A
Component and/or Version: Reifendruck 3 H05 0100
Software Coding: 0062725
Work Shop Code: WSC 02335 785 00200
VCID: 221DE5CF48C9B4DB915-8076
1 Fault Found:

01521 - Sensor for Tire Pressure
004 - No Signal/Communication - MIL ON
Freeze Frame:
Fault Status: 11100100
Fault Priority: 3
Fault Frequency: 115
Reset counter: 167
Mileage: 159020 km
Time Indication: 0
Date: 2019.01.27
Time: 16:08:44

         Freeze Frame:
                (no units): 30.0
                Voltage: 13.80 V
                (no units): 61.0
                    Not Recogn.
                    Not Recogn.
                    Not Recogn.
                    Not Recogn.

Friday,01,July,2022,16:03:03:25692
VCDS – Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 22.3.1.4 (x64) HEX-V2 CB: 0.4615.4
Data version: 20220407 DS337.0

VIN: WAUGN94F37N089902 License Plate:

            Address 01: Engine  (4F1 910 552 A)

16:03:00 Group 001: General
0 /min Engine Speed (G28)
93.0°C Coolant Temperature (G62)
0.0 % Lambda Control Bank 1/2
0.0 % Lambda Control Bank 3/4
Wednesday,16,November,2022,21:13:25:25692
VCDS – Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 22.10.0.1 (x64) HEX-V2 CB: 0.4623.4
Data version: 20221026 DS344.0

VIN: WAUGN94F37N089902 License Plate:

            Address 11: Engine II  (4F1 910 552 A)

21:13:22
-7.0 % Lambda Control Bank 1/2
-10.5 % Lambda Control Bank 3/4
0 Misfire Counter
Enabled Misfire Recognition
0 Misfire Counter Cylinder 1
0 Misfire Counter Cylinder 2
0 Misfire Counter Cylinder 3
0 Misfire Counter Cylinder 4
0 Misfire Counter Cylinder 5
34.80 bar Fuel Rail Pressure (actual)
0.00 bar Fuel Rail Pressure (spec.)
3 Fuel Pressure Control Status
Monday,21,November,2022,12:43:24:25692
VCDS – Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 22.10.0.1 (x64) HEX-V2 CB: 0.4623.4
Data version: 20221026 DS344.0

VIN: WAUGN94F37N089902 License Plate:

            Address 11: Engine II  (4F1 910 552 A)

12:43:22 Group 031: Lambda Control (Lambda Sensor Voltages)
0.99 Lambda Control Bank 3 (actual)
1.00 Lambda Control Bank 3 (specified)
1.00 Lambda Control Bank 4 (actual)
1.00 Lambda Control Bank 4 (specified)

12:43:22 Group 032: Lambda Control (Mixture Adaptation)
-0.4 % Adaptation (Idle) Bank 3 Sensor 1
-4.7 % Adaptation (Partial) Bank 3 Sensor 1
-0.1 % Adaptation (Idle) Bank 4 Sensor 1
-3.1 % Adaptation (Partial) Bank 4 Sensor 1
Monday,21,November,2022,12:52:28:25692
VCDS – Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 22.10.0.1 (x64) HEX-V2 CB: 0.4623.4
Data version: 20221026 DS344.0

VIN: WAUGN94F37N089902 License Plate:

            Address 11: Engine II  (4F1 910 552 A)

12:52:20
-2.7 % Lambda Control Bank 1/2
2.3 % Lambda Control Bank 3/4
15.8 % Engine Load
0 Misfire Counter
Enabled Misfire Recognition
0 Misfire Counter Cylinder 3
-0.4 % Adaptation (Idle) Bank 3 Sensor 1
-4.7 % Adaptation (Partial) Bank 3 Sensor 1
0.0 % Adaptation (Idle) Bank 4 Sensor 1
-2.7 % Adaptation (Partial) Bank 4 Sensor 1
34.20 bar Fuel Rail Pressure (spec.)
34.99 bar Fuel Rail Pressure (actual)
Saturday,21,January,2023,11:40:28:25692
VCDS – Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 22.10.0.1 (x64) HEX-V2 CB: 0.4623.4
Data version: 20221026 DS344.0

VIN: WAUGN94F37N089902 License Plate:

            Address 11: Engine II  (4F1 910 552 A)

11:40:24
1 Misfire Counter
Enabled Misfire Recognition
0 Misfire Counter Cylinder 1
1 Misfire Counter Cylinder 2
0 Misfire Counter Cylinder 3
0 Misfire Counter Cylinder 4
0 Misfire Counter Cylinder 5
0 Misfire Counter Cylinder 6
0 Misfire Counter Cylinder 7
0 Misfire Counter Cylinder 8
0 Misfire Counter Cylinder 9
0 Misfire Counter Cylinder 10
Saturday,21,January,2023,14:38:06:25692
VCDS – Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 22.10.0.1 (x64) HEX-V2 CB: 0.4623.4
Data version: 20221026 DS344.0

VIN: WAUGN94F37N089902 License Plate:

            Address 01: Engine       Labels: 07L-910-552-BSM1.clb

Control Module Part Number: 4F1 910 552 A HW: 4F1 907 552
Component and/or Version: 5.2L V10/4V FSI ª0040
Software Coding: 01050009190F0160
Work Shop Code: WSC 66565 257 00032
VCID: 221DE5CF48C9B4DBDD6-8076
1 Fault Found:

008567 - Bank 1; System Too Lean off Idle
P2177 - 001 - - Intermittent
Freeze Frame:
Fault Status: 00100001
Fault Priority: 0
Fault Frequency: 4
Reset counter: 255
Mileage: 173137 km
Time Indication: 0
Date: 2022.11.10
Time: 14:21:34

         Freeze Frame:
                RPM: 1674 /min
                Load: 37.2 %
                Speed: 34.0 km/h
                Temperature: 91.0°C
                Temperature: 21.0°C
                Absolute Pres.: 950.0 mbar
                Voltage: 13.843 V

Readiness: 0000 0000

#2

It’s not if the injectors will be bad it’s when will they be bad. It’s not a terribly long time until the injectors need to be serviced. Missfires are one of the signs of bad or carboned up injectors.

You can check the fuel trims that can help give you some idea but overall. I’d say even if the missfires were not happening I would still suggest you get the injectors cleaned or replaced.

#3

Thank you very much for the reply. That’s the motivation I needed to tear into it. I will update the post when completed. Thanks again. Rob

#4

How did you run your smoke test? I had similar issues and thought my smoke test was fine. Found out I ran it incorrectly and had a vacuum leak at the throttle body whoch seems to be fairly common.

#5

That’s a good question and I probably didn’t do it right or thorough enough. Since I couldn’t find any how-to’s, I guessed. I removed the air/oil separator and ran it through the rubber line that runs below the intake manifold. That was the line I suspected. I’d love to know where the best place is to connect if you could offer any guidance on that. The hoses that run from the valve cover are new but there are a billion other hoses I’m not sure about.
I did spray starter fluid at the gasket locations around the throttle body, manifold and plenum and it didn’t seem to impact the idle at all.
Thank you.

#6

It does seem to start once the car is up to temp but it could be because I don’t stomp on it until it’s warmed up.

#7

I kept the pcv attached. Rubber gloves over the intake tubes and ran the smoke machine through the hose at the front on the intake manifold. Press the gas a couple of times to open the throttle bodies as well. The rubber gloves should be filled with smoke.

#8

I did another smoke test in the way you mentioned and still saw no leaks.
So I finally got the courage to start removing the intake to get to the fuel injectors. :flushed: . It’s probably going to take me a few weeks because I’m moving slow and very carefully. I will eventually report back…

#9

image
image1576×2100 1000 KB

Update:
I can confirm that fuel injectors 2 and 3 shown on the left are bad or still clogged inside. This is after a lot of ultrasonic cleaning. All other injectors are even after ultrasonic cleaning. Interestingly, injector 3 had a paint mark on it like it was used. I was surprised how bad 3 was, but it had been missing quite a bit as well. I’m going to try and replace the filters and see if that works. If not, I’ll buy injectors.

#10

Update:
3D printed some injector adapters to backflow injectors. Same two proved bad even after backflow cleaning. Ordered two new injectors.
Injector filter baskets were gone. Only the brass and a tiny bit of plastic remained. Ordered and installed new stainless screens per other post on this site. Flow tested injectors again. No change.
Reassembled injector Teflon gaskets and gasket kit. Injectors are ready to be reinstalled, BUT…

I’m taking a detour and going to walnut blast the valves. The previous owner said they were done about 20k miles ago which looks to be true since I spent about 2 hours painstakingly cleaning all the old walnut media. 3D printed media blasting adapter. Cleaning valves next weekend…
Have a great week!

#11

WOW those injectors were in terrible condition. I think members really need to be aware of just how bad these injectors can be when they age.

That looks like almost 20% down on flow after cleaning. Is that about right?

#12

Still cleaning the valves; I’m slow…lol

I’m wondering if there is a reason why people don’t use a steam cleaner to clean off the carbon? Steam makes quick work of removing old grease and dirt from the outside of engine. I would think that as long as you vacuumed out the water, use carb cleaner and compressed air to remove all the water, it should work, right? Thoughts? I’m guessing I’m missing something or someone would have done it by now.

#13

I think that may be a great idea to try steam. I always use chemicals as the walnuts go everywhere.

#14

Okay, I tried steam and it worked okay, but I wouldn’t recommend it over chemicals + walnut blasting + picks + bamboo skewers + brushes + a lot of time. 3 more cylinders to go. Hoping to put this monster back together next weekend.

#15

Got to the last cylinder and the valve was not completely sealed so I spent about 2 hours meticulously cleaning the valve seat and part of valve that touches the seat, while keeping the cylinder as clean as possible with vacuum and compressed air. I won’t be starting it until I get a endoscope down in the cylinder to see if there is any dirt. My endoscope died during this process of course. There was just the tiniest bit of hardened carbon causing an air leak. I would say if you have misfires after cleaning, then do a leak down test. I will be doing a leak down test on each cylinder before putting everything back together.
I ended up buying a 24mm oil filter cap socket at a local auto parts store for $10 which fits perfect on the alternator bolt to rotate the engine. I also used a set of “spoon” type scrapers which work great for cleaning off carbon. Just be super careful and don’t muscle it.

1 Like
#16

I was wondering if there is a restart procedure after removing and cleaning injectors and cleaning intake valves? I was thinking about pressurizing the fuel lines to see if there are any leaks. Any tips or hints? Thank you!

#17

I got the car buttoned up tonight. I charged the fuel system and heard a small leak at a fuel line fitting. Thankfully I could just barely reach it with a 17mm box end wrench. Once I got that tightened a bit more, the leak was gone. So I started the car and the EPS light came on for a second but cleared out quickly. No check engine light. It was running really smoothly but I still smelled gas. I found that the electric plug at the drivers side high pressure fuel pump had fuel dripping out of it. Has anyone had this happen? I’m guessing the seal at the electrical plug to the pump is failing? I cleaned it up, started the car again and it wasn’t leaking this time. The car seems to be running great, which I’m super excited about, but I’d like to fix the fuel leak. I did some searching on the forums and looks like I may not be the only one that has had this issue.

#18

Well…uh…I had forgotten to connect the evap purge valve electrical connector and I may or may not have connected one of the MAFS. Doh! Lol. I’m guessing that is the reason for the leak and throwing the EPC code for a second. Must have been in closed loop. Ran perfectly in closed loop. Lol. Seems to be fine now and running smooth. I need to clear a few voltage related codes and hope that’s it.

#19

Great to hear it’s all back up and running. A lot of work so it’s not uncommon if you’ve not taken off the intake several times to catch everything. It can take a day or two for the ECU and everything to settle.

The fuel leak is something I’d keep an eye on however. It’s common to have pesky leaks but you want to be careful and tend to them quickly. HpFp pumps have been known to leak past the seals and some have reported the leak just as you have. So keep an eye on that.

1 Like
#20

Morning,
In my past experiences I was able to remove solenoid/sensor and reseal using new O-rings from one of my Caterpillar O-ring kits, also while I was at it I removed complete HpFp assy and ringed lower seal to head… simple and effective fix… Although in the past I have had to replace 1 solenoid/sensor due to leaking from center of cracked plastic housing… Good luck glad to hear you r progressing!!

1 Like