Hard idle misfires cyl 2/3 - need some help

A6 All/ S6 All
#1

I’ve been dealing with misfire issues for sometime now with my 07 S6.

  1. Last month, had misfires higher RPM and axle vibration. Replaced the axle and took the car out for a run. Full power, ran strong. Fast forward a week, CEL came on for misfire during some throttle @4k RPM - Got worse and could not go quarter throttle at highway speed without a flashing CEL.

Found a couple cracks in the oil separator hose (long over intake plenum) wrapped cracks, seems OK but will need to order a new replacement to make sure - $200 plastic part.

  1. Pulled codes - cyl 2,6,7,8 all misfire CEL at 4-5k RPM - car was idling OK, and could be driven lightly. Got worse as engine ambient temp increased - could be the oil separator wrap loosening up with heat.

Replaced 2,6,7,8 plugs and swapped coil packs. Plug tubes had oil up to mid of plug. Can’t tell if valve cover or lower. Re wrapped oil separator hose (seems sealed - can’t hear or feel air) and now car won’t idle without flashing CEL - very rough. Pulled codes and 2,3 both misfire at 700-800 idle speed.

I’ve checked all vac lines I can find (cannot reach line under IM) and don’t see any splits.

Pulled, swapped and tried different plugs and coils on 2,3.

Unless the oil separator hose is leaking vacuum that I can’t feel/hear, along with the higher RPM misfires mentioned above, it must be Injector related; weak higher RPM, maybe leaky at idle.? Car had a carbon cleaning a year ago.

Thoughts would be appreciated. I’m most likely bound to order 5 injectors Monday, luckily at cost ($70 each) for 2,3,6,7,8 and see - since no other cyls were suspect yet via vagcom.

Thanks guys!

#2

I think your thought process is on the right track. If you did not change out the injectors when the carbon cleaning was done last year then this is a good start.

Last August I had a dead miss on cylinder 1 when driving home one night. The week prior I had changed out all plugs and coils and was a little confused as to what was going on. I unplugged the harness from #1 and then plugged it back in and all was well again and hasn’t acted up since. Doubt this is what’s going on in your situation but figured it was worth mentioning.

#3

I do have an audible tick/tap 2k+ that increases with RPM - I can’t tell what cyl it’s coming from, but a friend thought perhaps it may be timing chain related - would a timing failure cause the codes below?

Address 11: Engine II Labels: Redir Fail!
Part No SW: 4F1 910 552 A HW: 4F1 907 552
Component: 5.2L V10/4V FSI ª0040
Revision: 59H14— Serial number:
Coding: 01050009190F0160
Shop #: WSC 02335 785 00200
VCID: 2241E5D7FDDA0D51DF-8076

3 Faults Found:
000768 - Random/Multiple Cylinder Misfire Detected
P0300 - 001 - - MIL ON
Freeze Frame:
Fault Status: 11100001
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 188985 km
Time Indication: 0
Date: 2017.06.09
Time: 16:43:53

         Freeze Frame:
                RPM: 662 /min
                Load: 30.2 %
                Speed: 0.0 km/h
                Temperature: 57.0°C
                Temperature: 34.0°C
                Absolute Pres.: 950.0 mbar
                Voltage: 12.954 V

000770 - Cylinder 2
P0302 - 001 - Misfire Detected - MIL ON
Freeze Frame:
Fault Status: 11100001
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 188985 km
Time Indication: 0
Date: 2017.06.09
Time: 16:43:53

000771 - Cylinder 3
P0303 - 001 - Misfire Detected
Freeze Frame:
Fault Status: 01100001
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 188985 km
Time Indication: 0
Date: 2017.06.10
Time: 10:02:51

         Freeze Frame:
                RPM: 754 /min
                Load: 28.6 %
                Speed: 0.0 km/h
                Temperature: 40.0°C
                Temperature: 24.0°C
                Absolute Pres.: 960.0 mbar
                Voltage: 13.462 V
#4

if it were timing chain, at least 1 whole bank would be experiencing this. flaps ok in manifold?

#5

That’s good to know.

Unsure about the flaps. I had one flap stuck code a few weeks ago. I’d assume if that was stuck I’d have a code pretty quickly come up?

Any way to check by hand or inspect visually?

I do have the injectors on the way so I’ll be able to check the flapper when the IM is off.

#6

As greg mentioned I doubt it is the chain. Generally if the chain makes noise its on start up and if you were really having chain issues where you could hear it you would probably have codes by now.

A good way to check to see if you have a vac leak is to check the fuel trims in vag com and report back what they are.

Your misfire codes are recording at idle so that could be a vac leak issue but I wouldn’t shy away from getting new injectors as they are usually the sorce of a lot of issues. Even if you don’t have injector issues it would still be a good idea to either service or get new ones.

Ticking is always hard to help with unless you can hear it.

#7

Sounds like vac leak. I’ll see if I can get the part number for the last part I had to get replaced.

#8

Thanks, Justincredible.

I wasn’t able to pin point a vac leak however I didn’t view trim levels either before starting to remove the IM. It’s pretty much out at this point. My 10mm 12pt bit was too long and not able to get in to remove the engine hoist mounts. Will have a bit Sunday/Monday and finish it up. I’m also not able to get my hands behind the nose to successfully unclip the IM plugs. It looks like there is plenty of slack in the harness wiring to come up and out with the IM then have a pair of hands ready to unclip them. Hopefully I’m right about that. It’s near impossible right now.

I’ve got 5 injectors coming, I should have just done 10 (kicking myself now) but I can have those I pull cleaned and flow tested if other cyls act up.

Have a new oil separator hose as well and will inspect the lower vac line that runs under the IM

Side now - how best to inspect the IM flap for damage or sticking?

Thanks guys!

#9

could someone help assist with injector removal procedure? I’m not used to this type of rail/injector setup. The rail is out, I have access to the injectors. I’ve bent back the metal tabs and removed the metal collar. How do you pull the injector?

Car is apart right now and appreciate the quick help!

#10

when they are not stuck, a good tug with the hand will pop em out, usually there is some corrosion in there. I jsut very very careuflly worked a flat head screwdriver around it enough till it came out. I went too hard on one injector in one spot and cracked the body (JB welded it and it has been fine, but still)

#11

The OEM way is with a slide hammer type of tool. Since you probably dont have that you can use a slide hammer if you have one as you want to pull right up.

If not here is what I do and I have never had any brake or give me too many issues.
First off good for you on getting the tabs out of the way almost no one does that and that is part of proper removal.

You can prime the area with a little penitration lube and I would spray that around the bottom of the injectors. I like to pull out the spark plugs and spray a little oil into each cylinder Im attempting to pull the injectors on put the plugs back in and crank over the motor. this causes cylinder pressure to rise and helps push on the bottom of the injectors. The adding the oil adds cylinder pressure past 200psi and its like getting help from the bottom. Its always best to make sure you have someone in the car cranking while your working on the injectors from up top. After you do that a few times slowly work the injectors back and forth as you slightly spin and pull up.