Heyst

2005.5 A8L face lift. 4.2.
driving down the highway my car started to bog and die, then get a blast of power and then eventually stall out. I pulled codes P2234, P2231, P2415, P2414 but have not had a chance to scan with VCDS.
Basically both of my pre-cat o2 sensors **** the bed, or at least are reporting they did but to have both go at the same time is odd, no? Really hoping it's not an ECM.

It's as if one of the fuel pumps died.

Car will not start now. Cranks but no start.

I haven't seen these codes before so maybe someone can chime in here on a direction I should take. Thank you in advance

TSHong

First step would be to isolate it to either fuel or ignition issue and then drill down. A bad O2 will not prevent your car from running. A bad O2 can damage other components over the long haul by creating a rich or lean mixture.

Heyst

I've had lean codes for ages, replaced the whole nine. Stopped shy of replacing cats (had bad coil packs for a month or two and fuel ratio was rich) so maybe they're finally clogged after all this time. might not be the issue but certainly not helping.

​​​​​​Both STFT and LTFT read + and I could smell it was lean. After 12 years it sounds about right to replace the fuel pumps. I might only swing for the right hand side pump. Depending who you ask, it's the pump that keeps the car running and the other (left) takes on any additional load and transfers fuel.

ltooz_a6_a8_q7

Some wires/connectors/ vacuum hoses popped out due to engine vibrations or pot holes.
Look under the throttle body and the FI vacuum hoses.
Never had bad fuel pumps with any of my Audi's even @ 175k miles.
The codes will show up if the fuel and ignition systems are not well.
Cheers,
Louis

Shark_V8

Start with fuel pressure test, fuel supply. Hiway driving is high flow demand, due to steady horsepower output. A lot like a boat actually, which drinks fuel.

A8's are known for R-side fuel pumps aren't they? Mine was replaced.

Panelhead

Brozee

+1 Panelhead.

I recently had one go out of no where. It was odd and the car would struggle and surge. Scanned it with VCDS and noticed one was firing incorrectly. Replaced the spark plug and the coil pack and all is working great now. Ended up purchasing the coil pack from the dealer and it was similar if not cheaper than buying OEM online.

Heyst

Thank you for the replies.
luckily I have an old 01 GMC Sonoma to boot around in while my car sits so I'm in no rush this go around.

At this point the car will no longer will start. It will roll over but not fire up. I do not hear fuel pump priming but I do hear one struggling loudly as I crank with key in ignition. I'll start to look into VCDS today.
All of my Coil packs are brand new r8's. All spark plugs are new (maybe 1000 kms on them). Fuel filter is somewhat new. I haven't let the tank drop below 1/8th. I had to replace valve cover gaskets and coil tensioner gaskets recently but I highly doubt there is a correlation.

Basically on the highway it was like a fuel cut off.. Engine RPM slowly dropped to around 1000 and then kicked in up until about 3300 and would drop with eventually stalling. I'll scan and get back.
It was a +30°C day and she was working great.

ScottCNelson

Do you see these four letters:
A
U
D
I

If so, there's your problem.

Heyst

For what it's worth, I replaced the right side fuel pump. The car fires right up now. Got a whole new pump unit with the hoses for $340 Canadian.

Once you open the tank (no special tools needed, caution if you use a Flathead screwdriver and a hammer to knock the ring counter clockwise *potential sparks from steel on steel*) there will be a spider web of hoses.

Examine your new pump and the hoses on it, then undo the old ones in the gas tank. They're secured by a clip, and you push that little button in to pop it off.

Not only are there hoses, but also a few other attachments on the pump assembly that need to be unclipped and set aside. Just take a look and you'll figure out how easily they come undone.

Big note, the longest hose attached to the pump housing actually had the connection in the left side fuel tank sooooo yes you have to open that side up just for that one.

Whole procedure took an hour. Now that I'm familiar it could take maybe 15 minutes.