S6 V8 AHK misfire when warm

[Harvester]

Hello guys , I am new here and I dont have thread on ,,Members cars,, section yet, but it will change soon . Maybe .
I have a problem , I bought an Audi S6 Plus sedan for very reasonable price but with ,,CAT,, control light issue .
I have following problem.
When i start a car , cold , everything runs well and smooth , the car got a power , no problems at all .
When it is warm - warmer for example after 20-30 minutes driving in this weather the engine starts shaking , has no power , i can not go on throttle.
Diagnostic says : O2 sensor no singnal - changed both today but still the same .
Misfire on 3 and 7 cylinder - i changed coilpacks and sparkplugs between each other but misfire doesnt move to other cylinders , so i think this is not the way to solve the problem. Tomorrow I am gonna check injectors and harness.

But I have still some questions ... isnt it a bit weird that i have misfire directly on the oposite cylinders ? And could it be harness or what when its doing only when engine is warm ?

I really appreciate your help ...thanks
I am sorry for my bad English..

[rs200]

there is a multiple misfire on your ignition coils or POS terminals.
the best option is to replace all 8 coils (use FSI coils BERU ZSE 033) and your problem will gone forever !

just like I did on my s8 before few weeks !

[rs200]

if you want just fix it for some time you need to change one POS terminal.
here is picture of both POSs

http://i768.photobucket.com/albums/xx329/NaijaGuy/S8-Powered%20Audi%20A4%20Touring%20Car/260220121176.jpg

[Harvester]

Thank you very much.
Where is the POS terminal located ?
Do you think coils will solve the problem , even the misfire didnt move to other cylinder when I swap the old (current) coils between each other .
The misfire was still on 3 and 7 .
I m gonna chceck POS terminal today.

[rs200]

both pos terminal is faulti and 2 coils dont produce ignition... your engine work on 6 cilinders... there are 2 pos. one is for 1467 coil and other is for 2358...
take out all 8 coils and look the rubbers wich is around sparks.. they must be good.. not broken..
if they are broken than you need to change this rubbers... but FSI coil are cheeper than this rubbers. than it is normal that you will change it and newer ever had this problem..

[Harvester]

I hope problem is found . Injectors on these two cylinders doesnt work . Do you think it could by whole problem ?

[rs200]

yes it could also be a problem.. but in 2 cases (my s8 and friends A8 both are 4.2 32v) there was a issue with coils and POS terminals !
so you change 2 injectors and now is fine?

[Harvester]

Yes I have changed both injectors and it seems to be fine. I have to do more repairs , due to maintenance and damages.

[rs200]

ok.. perfect. important is that you solve the problem !
are your injectors black or grey ?

[Harvester]

Injectors are ...if i remeber grey and they are 199cc for sure . I have spare injectors from classic S6 , the same shape , but I cannot use it because they are only 180cc .

[rs200]

the same is with audi A8 and S8 .. black is on A8 .. grey are on S8.

[Harvester]

Good to know .