silverd2

It seems that your car does just have 2 O2 sensors...the forward ones, then temp sensors at the cats, where newer cars have secondary. The temp sensors probably do just a basic check of "rich or lean"...too hot = lean, cooler = rich.

But, as long as 02 sensors have existed, I have never seen one (or all) cause misfires...no matter how failed, shorted or altogether disconnected. They are designed to simply trim fuel mixture within a predetermined "map". When filed, even in much older systems, the mixture is supposed to fall into a default (limp) mode..usually at the rich end of the "map".

Disconnecting them may have altered the behavior of your misfiring problem, but my guess is that the 02 sensors have nothing to do with such severe misfiring...and you co

I may have missed it in an earlier post of yours, but have you considered the power output stages (2 ignition control modules) that send signals to the coils. This isn't my top choice either, because both modules would have to be bad to get the codes you listed...one module fires cylinders 2,3,5 & 8...the other fires 1,4,6 & 7.

Even though you've tested the fuel pump outside the car, the symptoms still scream of fuel starvation problem...bad fuel pump (or similar starvation problem) does not throw a code of it's own...just the problems it leads too.

I would also wonder about an ECM or ECM wiring (corroded connection) problem...water in the electronics box, past or present?

...sorry if you've already eliminated that, but I just don't see the 02 sensors do this...but I've been wrong before

Proph3t

Ok well one sensor wasn't very active while the other was, so its more likely the inactive one has the issue.

The thing I cant understand is that it's now unplugged, and still I'm getting CAT light and cylinder 1 missing, which wasnt the case when I first unplugged it, it was perfect, just a little rich as expected. I know the coil and injector along with valves and timing etc, are actually good as it revved cleanly all the way through to red line without a problem; whihc I did just to ensure the missing was load or rev based. I'll try unplugging the other oxygen sensor and take them completely out of the picture. See if it will at least drive again.

Only thing I havent looked in detail is the ignition amps up high on the left of the engine bay, next to the washer bottle. Apparently these can act up and give very similar symptoms. (Although the B1 S1 oxygen sensor is the one that failed in the logs...)

Anyone shed more light on those for me, or maybe have some more tests to go through.

Thank you.

Proph3t

Sorry, just saw your post sneak in the there SilverD2...

I too am no longer pointing the finger at the oxygen sensors like I first was. It indeed did change the situation, but it soon returned to the same old symptoms.

If the power output stages (I called them ignition amps, although they dont amplify anything) are not specific to the left and right bank then I could probably eliminate them as it been pretty solid at cylinder 1, then 2 sometimes, then the entire first bank, then cylinder 5, doesnt line up with POS layout.

I still have the fuel pump and a vacuum leak in the back on my mind. Might need to reinvestigate the fuel pump. I have a snake camera now, so can verify the seating of all of that in the tank.

What symptoms do vacuum leaks give from the large breather tubes. They all look solid and sealed to me, but just asking in case.

I just find it very odd that it can start and sit there fine, then start missing on cylinder 1, then warm up and start missing on random ones.

Doing my head in. It can only be fuel, air or spark. Simple right? :P

Proph3t

So another Saturday sitting in front of VAGcom smelling like fuel and anguish...

I've installed new BOSCH spark plugs. I don't want to blame the oxygen sensor anymore, but the code keeps appearing, and now as a "circuit malfunction". Car doesn't seem happy with or without it, and now basically won't idle at all. Codes below were from last weekend when it was warm and wouldn't get up driveway, with oxygen sensor unplugged...before I gave up.

5 Faults Found:
16518 - Oxygen (Lambda) Sensor B1 S1: No Activity
P0134 - 35-00 - -
17541 - O2 Sensor Heating Circuit, Bank1 +2 - Sensor 1, Electrical Malfunction
P1133 - 35-00 -
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 - -
16685 - Cylinder 1: Misfire Detected
P0301 - 35-00 -
16686 - Cylinder 2: Misfire Detected
P0302 - 35-00 - -

Today, with new spark plugs and oxygen sensor plugged in...
3 Faults Found:
16514 - Oxygen (Lambda) Sensor B1 S1: Malfunction in Circuit
P0130 - 35-10 - - - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 - -
16689 - Cylinder 5: Misfire Detected
P0305 - 35-00 - -

Started perfectly after a week of sitting. Ran ok but with a slight audible misfire on 1 or 2 cylinders every now and then, then it fell into full-on stumbling and CAT light as it came off warmup. Dad said it was blowing dark smoke, and smelt rich.

Unplugged battery for an hour in an attempt to reset the ECU. No different. "Running" on a few cylinders, no codes.

Tank has been at 1/2 tank with all these problems, so I added 15 litres of 98 octane. Went to start now has a flat battery...so it's charging overnight.

sighhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhh

yrk2.7t@curbside

I wonder if you have a clogged or failing catalytic converter?

That would be blocking some of the exhaust and could cause a mis-fire.

If you look are channels 13, 14 and 15 (IIRC) do you have mis-fire counters there?

silverd2

From your latest post, it's sounding like something is interrupting spark...not fuel starvation or a vacuum leak.
Black smoke is unburnt fuel (rich smell). That can only be a few things and I think you've eliminated plugs and coils (and POS's?)...coils usually only go bad 1 at a time...NOT multiple misfires.

02 sensors operate within a map and have a default setting that would not allow black unburnt fuel smoke.

Bad MAF can sometimes cause stalling and other complications, but you "should" get an MAF specific code. Plus I didn't think they could fail to the point of black smoke...on many cars, you can unplug them and the car will continue to run on a default setting...not sure on a D2(?)

Just theorizing, but: That leaves the ECU (where the spark signal originates), it's connections and wiring to the the POS's..and their wiring on to the coils.

Proph3t

I've decided to give up digging for solutions and claim it under flood damage on my car insurance.

If anyone remembers, way back, my wife was stuck in flash flooding in the car, and although the water wasnt terribly deep on the road, she had to leave the car for safety reasons and it was left in a traffic jam of cars over night unable to move do to the water on all surrounding streets, I had to wade through waist deep water to get to her and back. The water appeared to have been briefly as high as the headlights at one point where the car was, maybe due to wash from other cars etc...but after everything I've checked, and other things now happening to the car, I'm assuming water in the ECU or wiring harness and dash is causing the dramas. It was lucky it got home in the first place...where it has died a slow electrical death.

I've found my stereo has stopped working and just crackles on one speaker (rear drivers side door); remote central locking stopped working; interior lights dont turn on from all the doors opening, only drivers; alarm going off by itself; and also both the power steering and alternator bearings sound stuffed (howling etc)... funny coincidence, since the alternator is only 6mths old. I wasn't sure at the time of looking, but the insulation up under the dash felt wet, but I thought it was just cold, but on a hot sunny day the inside of the windscreen fogs up...a good sign water has been in there.

Apparently the insurance company I'm with has a good history of writing-off any cars that get water up to the door sills, and this was above that.

I hate to see her go like this, but I also hate to have a car like her and not enjoy her.

Thanks to everyone that has helped and spent time going through all my long winded posts. Really do appreciate it guys.

Now I might finally get that old Mk1 Golf I've been whining about

Adjuster

Another A8 bites the dust.

There are not that many folks, and the more that go away, the more rare our old cars get.

Proph3t

The fact there aren't many in the world, let alone in Australia, was the biggest issue with resolving issues, getting parts or any sort of mechanical assistance. Even the Audi dealer wouldn't touch it because they "had no trained staff for that model". I think I've seen 3 other D2s other than mine in all my travels of Australia, a black facelifted one lived briefly in my apartment complex, but it promptly vanished. Sad really, Audrey was a beautiful car...but hey the insurance company may fix her up yet. It's Murphy's law that she didn't misfire getting onto the flat bed this morning, but I'm sure she'll erupt into a flurry of misfires and codes eventually for them.

I'd hate to see her scrapped, but its best for my family and I that they do a write off. We cant afford something getting unreliable with a toddler, and a baby on the way in December.