S4 B7 end of the road or restoration project?

[DrNutt]

Gutted. My beloved 4.2 V8 has just skipped a tooth due to the famous tensioner problem. Thankfully i wasn't 'driving' it when it happened but it's misfiring on all 4 cylinders on the driver's side but no valves etc have been damaged as far as i can tell.

I checked plugs and coils but issue remains on that side and after inspection by a local garage it's fairly conclusive what the issue is.

What would you do? Future resoration project or call it a day? The quote was eyewatering!

 

cheers!

 

 

[Magnet]

Hello Rob,

Sorry to hear of your problem. ‘No valves etc. damaged….’. The best way to confirm that is to get a compression test carried out on that bank to hopefully confirm your belief. That has to be your starting point for considering the car’s future. 
Kind regards,

Gareth. 

[DrNutt]

Thanks Gareth, anny suggestions re welcome at this stage so will make that my first mission just to be certain.

I think i will probably sell it to someone with more time/tools/experience on their hands but naturally want to be open about the condition of the poor thing!

Shame really, 'twas (still is) a glorious wagon!

Cheers!

Rob,

Edited October 17, 2024 by DrNutt

[Steve Q]

On 10/16/2024 at 3:05 PM, DrNutt said:

Gutted. My beloved 4.2 V8 has just skipped a tooth due to the famous tensioner problem. Thankfully i wasn't 'driving' it when it happened but it's misfiring on all 4 cylinders on the driver's side but no valves etc have been damaged as far as i can tell.

I checked plugs and coils but issue remains on that side and after inspection by a local garage it's fairly conclusive what the issue is.

What would you do? Future resoration project or call it a day? The quote was eyewatering!

 

cheers!

 

 

I feel your pain as I'm.in a similar boat with my A6. Mines still off the road as the engine rebuild cost is eye watering. But finding a 2nd hand engine that'll work is just as hard as it all.has to be coded and work with the injection pump, ECU and instrument cluster. 

If you decide to put in a 2nd engine and you find someone who can do it plus coding please let me know as I'd be very interested. 

[DrNutt]

I have my mate coming round soon to help do the compression test, he’s had a few Audi V8s over the years so knows a thing or two!

I’ll let you know about the engine swap as it’s something I’ve also considered however you never really know the full history so may be false economy.

Tough one!

 

[Steve Q]

Definitely a tough one. My poor A6 has now sat nearly 2 years. As I say it's the coding nonsense that's the problem. Gone are the days where you fit any engine you like unfortunately 

[DrNutt]

So, my good mate and top mechanic had time to help me check the compression on the old V8 recently, so sit comfortably and i'll tell you a story 🙂

It was -5 degrees outside, the first half decent weekend of January...

I'd like to know if anyone has had this experience to help me identify if it's really a timing issue (slipped chain, loose chain or other)..

 

1. Compression test:

Step 1. remove fuse from fuel pump and ignition systems

Step 2. remove spark plugs one by one and crank over with compression test tool attached. Repeat for each cylinder.

Originally the OBD11 tool was showing random misfires on cylinders 1-4 (Driver's side bank in the UK) which was suggesting a broken chain tensioner or similar.

results: All cylinders except number 7 were recording around the 110psi mark after cranking over for about 5 seconds or so. Number 7 was reading around 50psi to start with, but the car has been sitting idle since October under cover. My good mate suggested putting just a small capful of oil down the hole, just enough to coat the surfaces, and after a few minutes it was back up to pressure, consistently too!

2. Test run:

We then replaced the fuses for ignition and fuel pumps to have another listen and run the OBD11 again. The good old thing started first time but was running rough as anything, but there was some obvious backfiring into the airbox.

OBD scanner showed only regular, consistent misfires on cylinder 1 this time (previously and consistently 1,2,3 & 4)

Questions please:

1. Does this still smell like timing chain tensioner broken/missing causing slight backfire into airbox or is there maybe some other air leak going on?

2. I'd like to check the cam positions, Are there timing marks on the front of the cams to help identify any positional issues or are these all on the back?

 

Thanks to all!

It may live again :)

Rob.

[cliffcoggin]

Tom.

110 psi seems a bit low for a modern engine, so I think it likely your valve stems are bent. The only way to be certain is to remove the heads and valves, then roll the stems on a flat surface. Any bend will be immediately obvious.

An increase in compression after putting some oil in the bore usually indicates a busted ring, so your problems may be worse than you think.

[DrNutt]

Thanks Tom!

I'm going to investigate further and see what i find. It was -5 out and the engine was stone cold while i was doing the test.

The car was initially getting up to temperature and running smooth until i got to the end of my road when it developed the misfire etc. Let's see... just trying to find what i can without having to take the engine out!

 

all the best!

 

 

[Magnet]

Hello Rob,

The recommended way to check compression is to remove all plugs before carrying out this procedure so the engine spins freely. 
As Cliff says 110psi is too low. Well worth repeating with the above procedure and you may find you get higher readings.

Kind regards,

Gareth.