Misfires and lack of timing correlation on both banks - have you looked at the crank position sensor? Just throwing the idea out there since (besides the mechanical bits) its one of a short list of items that would affect the operation of the entire engine.

 

I seem to remember saying somewhere back in the beginning of this thread that at some point you would be our resident guru by the time you got this figured out...

methinks you're there

 

Hey guys,
Crank Pos Sensor checked out OK way back when, but changed away, to rule it out. Not the problem.
Checked & changed out lots of items on my short list, now I'm into bigger bucks, including wasting $$ at a shop.
But keep throwing ideas my way because this problem lingers on.
Yeah I certainly might be the resident guru "once I figure out this issue". What a major PITA it has been nailing down the cause for this misfire. Paid the Audi shop big bucks do to what I've done 3 times before! They were certain it was timing & they redid it, checked cam chains (they said count was right)& reassembled only to have no change. They charged me full price anyway, even though they fixed nothing. Even had the ***** to charge me for new cam seals even though the ones in there were brand new!! I argued to cut me a break on the price since they didn't fix problem, but they wouldn't budge. They did recommend they keep the car longer to check out more items, but cost would continue to increase. Screw it. Hind sight shows it was a mistake taking it to this shop. Back in my garage, & under my control. Could have probably gotten new tensioners &/or ECU for $$ they charged to not fix the problem. I'll get over it...sometime. Just venting.
So has anyone had cam chain tensioners go bad, yet they still passed the various tests, resistance, voltage, solenoid activation?

 

Have you ohmed out the wiring harness from the #5 injector and coil pack to the ECU to be sure there's no damaged wiring that'd screw up the signal to fire? Also, you could try moving the #5 injector to cylinder 6 and see if the misfire stays put or moves. If you do this, be sure to use new injector o-rings each time you install them so you don't leak fuel.

Hope it works out fast man - it sucks chasing an issue like you've been doing with this one.

 

Hey AF! Guess what's back in my garage?
You got it, The A6. Since getting it back from the shop (un-fixed for $1300) my son's been driving it with the idle miss-fires. Now seems to only do it at idle with the a/c off. A/C on & miss-fires stop. Go figure. I suspect tensioners, because crank/cam phasing at 25° KW & spec says 0 °± 6.

So it's in garage because he said serpentine belt was squeaking. More like SCREAMING!
Popped hood open & noticed a/c pulley was twisted so that pulley axis is tilted. Pulley was a gnats hair was away from hitting the fan, & belt was ~ 1 rib off the tensioner. Here's some pics of the situation. This even snapped one of the studs that holds the bracket to the block. Having a really tough time drilling out the embedded stud, due to access.

So we saw several loose/missing bolts, misplaced timing covers, cracked sensor connectors, etc. that the shop is responsible for, because I know they were done correctly before, by me. It was wishful thinking that this Porche-Audi-BMW shop would fix what's broken rather than break what's not. I can't say whether they messed with the missing a/c compressor bolt that led to this mess, but I am suspicious. (Did they loosen compressor to get better accessto crank lock bolt? Who knows.) I thought of bitching at them, but no good would come of it. I can't prove they screwed with it & I won't trust them to fix it, even for free.
Anyway, I found a couple of places selling used brackets, so I'll pick up a replacement. The tough part is drilling out the stud in tight quarters.

 

What a pain... That is why I am so jaded when it comes to someone working on the car.

A couple of sources.

shokan.com/ for used parts.

genuineaudiparts.com for new parts.

Genuineaudiparts is audi of San Diego. Their new price on parts is dirt cheap compared to other dealerships and I was sometimes surprised by how cheap they were compared to some aftermarket and used parts.

 

So the ABS issue lingers on (among other unsolved issues), since the Module was repaired, but now have open or short in the circuit. I expect I need to chase the wires from ABS module plug to whereever? to find the problem. I don't know if these other electrial problems are related, but we have the W/W fluid low signal, even though it was replaced with new. And get Bulb Out signal, although every light bulb is working (except cluster right blinker indicator, the blinkers do work however).

01203 - Electrical Connection between ABS and Instrument Cluster
31-00 - Open or Short to Ground

This is progress, because I used to get can't communicate with ABS before module was repaired.

ABS wiring goes aft behind heatshields along frame by bank 2 & I can't yet see where they go from there. I expect they either go thru the firewall (to instrumentation cluster) or to ECU (then cluster).

So my question to anyone that has gotten this deep into chasing ABS wiring is: Do you know any specifics about where the ABS routes to when going from the ABS to cluster? Anyone have wiring diagrams handy for the ABS for A6 C5 2.7T?
I'll have to go thru my Bentely manual again to try & find this wiring diagram.

 

Still troubleshooting misfire codes, all cylinders, & cam/crank out of correlation, both banks.

Had a eureka moment when checking cam chain tensioner p/n's.
I have what I now know is the WRONG setup:
Bank 1 (PS, right): p/n 078-109-087C
Bank 2 (DS, left): p/n 078-109-088C

All sites I checked for new tensioners list them opposite, 8C right, 7C left.
So PO or Audi shop had switched tensioners L/R to R/L .
I know it wasn't me because I never had both banks off at the same time.

Can any of you C5 folks take a peek at your DS tensioner & confirm the p/n?

So this now has me thinking, if they switched the tensioners, did they switch the cams?
Good news is that you can't switch Exhaust cams, because they have the front spindle part that the TB sprocket attaches to.
Bad news is that it seems to me that you might be able to switch the Intake cams. I have to compare them more, as they are still installed.

Anyone have their valve covers off, or are familiar with the intake cam markings to confirm intake cams?
Both intake cams have 0781 stamped on them & my bank 1 also has BH, while Bank 2 has BJ stamps. These markings are on both sides of the center group of cam lobes.

So I can certainly swap the tensioner back to where they belong, but I need to know switch sides the intake cams go to.
Help is welcome.

 

THE FIX:
CAM CHAIN TENSIONERS WERE INSTALLED ON WRONG SIDES

Got the A6 back together, with the cam chain tensioners installed on the correct side. Cleared codes, & did a test drive.
NO MORE MISFIRES !!!!!!!!!!!!

This sure does make me happy, after all the work on trying to figure this problem out. Again, the multiple cylinder misfires & cam/crank out of correlation was there since we bought the car. Apparently PO, or his mechanic pulled the switch-a-roo on the cam chain tensioners L/R vs R/L. Every time I disassembled the cams, I did each side at a time, so I never had the chance to mix them up.
SO, lesson learned for anyone out there that has misfires on all cylinders & cam/crank out of correlation....check the p/n's of the tensioners to make sure they are on the correct side.
Certainly there could be other causes, but in hindsight, this is an easy one to rule out. Unfortunately, Audi did not make installation of the cam chain tensioners foolproof, so they could only install on the correct side. A simple move of a bolt hole would have done it.

The bad news is oil leaking near DS turbo. 1st inspection doesn't indicate it's from the valve covers, cam seals, or tensioner seals, but I'm hopeful that we just screwed up these seals, since the turbo wasn't leaking before we tackled this last repair effort.
Audi back into my garage, once again.

 

Thought I'd throw an update in here. A6 running great ever since the cam chain tensioners installed correctly. The DS oil leak was a leaky cam seal. fixed it & no more leak.
Just noticed the aux fan is not running. Start car, A/C on, fan not running. I jumped low side (1-2) pins for water temp sensor & fan not running. Ditto for high side (3-4 pins). Disconnected fan plug & put 12V across it, & fan does work.
So what's next step for checking what's broken?
Is this enought to conclude it's the fan control module, or are there some other checks I should do?
Fuses good on DS fuse box panel.