phistration

Hello all. I am looking for some suggestions. I have an 07 S8. Earlier this week when I was driving there was a slight hesitation when I was changing lanes and then the EPC light came on. The car seemed to drive normally afterwards. Later that day on my way howe the EPC light turned off. The next morning the car drove fine. That evening while diriving, the car hesitated and the EPC light came on. The next time it was driven the EPC light was on and the check engine light came on. When I went back to the car to pull codes just the check engine light was on. Additionally I have noticed that when I am doing a cold start and letting the car warm up the rpms increase as normal. When the rpms drop to normal the vehicle will idle a little rough for a few seconds then clear up. Below is the results of my scan.
Address 01: Engine Labels: Redir Fail!
Part No SW: 4E0 910 552 A HW: 4E0 907 552
Component: 5.2L V10/4V FSI ª0040
Revision: 5AH11--- Serial number: AUX3Z0F7705339
Coding: 01060009190F0160
Shop #: WSC 08212 444 83316
VCID: 2019E316C6CE6287BE5-8074

2 Faults Found:
000135 - Fuel Rail/System Pressure
P0087 - 008 - Too Low - Intermittent
Freeze Frame:
Fault Status: 00101000
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 294043 km
Time Indication: 0
Date: 2018.11.06
Time: 07:34:23

Freeze Frame:
RPM: 3267 /min
Load: 84.3 %
Speed: 118.0 km/h
Temperature: 96.0°C
Temperature: 20.0°C
Absolute Pres.: 960.0 mbar
Voltage: 13.335 V

000135 - Fuel Rail/System Pressure
P0087 - 002 - Too Low - Intermittent - MIL ON
Freeze Frame:
Fault Status: 10100010
Fault Priority: 0
Fault Frequency: 4
Reset counter: 255
Mileage: 294044 km
Time Indication: 0
Date: 2018.11.06
Time: 07:34:24

Freeze Frame:
RPM: 2519 /min
Load: 81.5 %
Speed: 100.0 km/h
Temperature: 92.0°C
Temperature: 9.0°C
Absolute Pres.: 980.0 mbar
Voltage: 13.843 V

Readiness: 0000 0000

Any help is appreciated. And yes I have done a search but I didn't find anything the quite fit my conditions.

PaulW

Without knowing anything about it....I would say you have an issue with your fuel system. I can't remember exactly what the EPC light does.....but on my 2010 Q5 it came on and when it did, it would shut down a cylinder and you would have a rough running engine. In the end, it was a spark plug that required replacement. I believe the engine management knows when the cylinder isn't firing and then shuts that cylinder down.

I do not know why it comes on with the S8.....but low fuel pressure could cause the same issue. Do you have the Bently? Can you look the code up?

phistration

Just an update. On the drive to work this morning I got the EPC light and the flashing check engine light. There is a reduction in power at any throttle more than about 1/4.

YESHONEY

The dreaded "limp mode"

Tstealth32

Could also be your fuel Injector. When mine went bad, I had the flashing engine light, loss of power and RPMS. My car had 140K miles when it went bad. If you do change these out, youll be able to clean the carbon from the intake valves as well.

MP4.2+6.0

1. Try a search first using those codes. (see sticky at top of D3 board...) Focus especially on D3 S8 and C6 S6 posts given they have same motor.

2. Having done #1, see this one for starters: https://www.audiworld.com/forums/a8-...-woes-2891007/

Notice your codes don't seem to be bank (cylinder head) specific. If they had been, I would say high pressure fuel pump (HPFP). But here, seems logical to suspect low pressure pump that would feed both sides from the tank. Known failure item from any D3 model. Replace fuel filter too.

Jack88

Given it's an S8, carbon fouling is a big issue and can lead to eventual running issues. At your mileage, if it has never been done, it should be. That said, I doubt that would cause a low fuel pressure code. Failing fuel pump, clogged fuel filter, and bad gas all come to mind as possibilities. I doubt it's a HPFP, those should affect one bank specifically unless they failed in unison, which would be ridiculous.

ScottCNelson

G410, Fuel Pumps, Fuel Filter, HPFPs, leaking fuel injector(s). I'd guess HPFPs.

phistration

Thanks for all of the replies. I doubt that it is carbon fouling as I just had that done along with all of the coolant hoses, oil filter housing gaskets, and intake replaced about 600 miles ago. If it was an injector causing the problem wouldn't I get a misfire on a particular bank?

ScottCNelson

Your code and symptoms are much more indicative of failing HPFPs. If it were me (and it has been), I'd start with the cheap and simple fixes, fuel filter and G410. The G410 is common enough a weak part to be notorious:

16471/P0087/000135 - Ross-Tech Wiki

If that doesn't fix it, HPFPs and cam followers did for me.