odoboyusa

[Edit]
To sum up quickly, so you don't have to read the whole thread, the answer is no, it was a broken guide, chains were not stretched at all.
PM me if you need help with this engine, I learned a lot about it.
[/Edit]


To make a long story short, I bought a 2006 A6 4.2 with a bad engine.
Bought a used engine on ebay. Verified that the engine has about 50k miles and the engine looks very clean inside.
After installing the replacement engine, I noticed a problem: the engine shakes around 1200 rpms (engine mounts are both new) and it has a knocking sound at 1800 rpms. No issues at idle. No codes as well. When driving on the freeway with the engine at 1800 rpm, i can feel a rhythmic tapping in the transmission shifter. it's correlated to the engine speed, not the road speed. The tapping sounds like it's coming from the rear of bank 1 (pass side). I looked inside the cylinders with an inspection camera, did a compression test, all looks good. I tried spinning the engine without the spark plugs, no noise. I think the knocking is ignition knock, not mechanical knock. The ignition timing graph seemed a bit odd.

Kept trying to diagnose the issue with vag com and what not and finally ended up going to the dealer for a diagnosis. They are saying the one of the timing chains is stretched. Quote for parts and labor is $11.000 (yes, eleven thousand). I told them no thanks and asked if this is normal (i know it's not) they said there's a campaign for the q7's which stretch chains left and right. I asked if there's any program to cover any part of this, they said no warranty = too bad. I now wish i had a friggin timing belt.

So, I'm pulling the engine back out, yey, and will overhaul the timing system. Anyone knows who can i talk to to get a parts list and maybe purchase the parts?
If anyone has any other things that i could check before pulling the engine, I would gladly do so.

I still own my 2000 twin turbo A6 and it has been awesome but after this episode and after seeing how little audi stands behind their crap quality engines, it's not likely i'll own another one without a warranty.

Thanks for your help in advance!

s4master1

For an engineer you throw yourself to the mercy of others a little too soon.
stretching chains at 50k bs, you may have a broken chain guide and as the adjuster is advancing timing, it knocks (1800) rpm.
can you get a reading on the timing?
can you elaborate on how simple the system should be according to you?
and lastly this is for my own amusement,
an engineer that builds entire factories and buys stuff like this is laughable.

odoboyusa

Thanks for your answer.
Your idea makes sense but it doesn't change the fact that the engine has to come out.
I can post a graph of the timing or I can look for something specific if you wish me to do so. I have a vcds so I can log anything else you might consider of interest.
Since the engine is coming out, I'm replacing everything in the timing chains drive system. Parts are already ordered.

As far as your side comments about throwing myself at the mercy of others too soon, it's your opinion. I tried everything I could think of before I handed it over. It was also important for me to get a written dealer diagnostic for reimbursement purposes.
And also for your amusement... I don't buy a project car like this because I have to, it's a hobby. I'm also not rich either. If the engine would have worked fine, I would have ended with the car considerably cheaper. But not all gambles can be winners. The dealer complemented me on the nice engine install. Kind of ironic though.
As far as how simple the system should be, no comment. I think others have said enough.

s4master1

See if you can get readings from channels 90,91,92 and 93 while at idle and at 1800-2200 rpm.
you can see the difference from one bank to the other in relation to the crank.

beep-beep

smart idea.

vlam04

you gotta take it easy s4master1. we don't know the whole story or what he has gone through. he probably just summarized the situation. no need to go on blast. heh heh.

s4master1

got it.
but blasting is all he/she is doing from smoking engineers to how simple a chain system should be.
I ask to elaborate at how simpler the system should be according to his/hers engineering skills.
I also just summarize my opinion.

odoboyusa

OK, I checked blocks 91 and 92 and it seems that the requested and actual position values follow each other closely, which means the cam adjusters are doing their work.
Looking at block 93 I see that the phase position for bank 1 is -7 and phase position for bank 2 is -5. From my previous reading I think -8 is the service limit for the timing system. Having the banks off by that much would explain a lot.
So, for my curiosity, why are both banks off? does that mean that the central chain might be stretched?
I'll be pulling that engine in the next couple weeks and I'll keep you updated.
Thank for the help and I do apologize for venting my frustration in my initial post

s4master1

looks to me that the tensioner on the passenger side has collapsed and the computer is compensating timing on bank 2.
the greater difference is in bank 1 and also the knocking on that side explain the theory of a failed tensioner.
please do let me know how it goes when the engine is out.

jujuC6

I have been diagnosed with a failed tesioner on my 3.2L by Audi and Indy. My question is, based on your experience with this is there any possible way that the tesioner can be replaced without dropping the engine or tranny? Thanks in advance.