Audi S4 4.2 B6 Help

[Moz18]

Hi guys new here! Love the site and I am looking forward to getting to know you guys!

so…. I have an Audi S4 4.2 B6 that has a severe issue 😔 car had random misfire on both bank and a camshaft fault. Confident it was timing chain I decided to do a compression test…

all cylinder came back around 195 psi apart from cylinder 2 & 8 which were both 0!

I have pulled the intake manifold so i could see the intake valves and on both cylinder 2 & 8 it appears 1 valve on each stays open a tiny bit? Any ideas what could be the cause? Here is a couple of photos of bank 1 cam shafts which seems out of time abit if im correct?

 

thanks in advance!!

Edited 4 hours ago by Moz18

[Magnet]

Welcome Mark,

How long have you owned the car, and how long have you had this sticking valve issue? 
Timing chain tension, and any chance it’s jumped a tooth or two? 
Regards,

Gareth. 
p.s. Can you be more specific with your location please? 
Large country is the U.K.! 

[cliffcoggin]

The timing chain has jumped a sprocket tooth as a result of stretching or collapse of its tensioner. When that happened at least two valves hit the piston crowns and bent the stems, hence they will not retract fully.

As if that's not bad enough there is a chance that the conrods have also been bent by impact with the valves, so you could have a very expensive repair bill ahead of you.

Timing chains don't fail abruptly. They give plenty of warning by way of chain slap before something serious happens, so I believe the growing problem has been ignored for a long time.

[Moz18]

Hi guys thanks for the responses! So I recently purchased the car for a VERY cheap price with this problem. (I love a gamble!) again paid very cheap!

the car still starts just misfires…

On both cylinder 2 and 8 it’s only 1 valve on each that is only very slightly open. Would the cams being out not cause this? 

I’m from the West Midlands by the way Magnet!

[cliffcoggin]

Now you know why the car was so cheap. A new or rebuilt engine is needed.

[Moz18]

Car was cheap as it was a family member … if the valve did indeed make contact with the piston, wouldn’t this have marked the piston? The piston in both 2 and 8 look perfectly fine?

[Magnet]

So it’s head off then, and replace at least 2 valves - they don’t stick if they aren’t slightly bent. New timing chain and associated components. Refit everything and keep fingers crossed that the work and expense has resulted in some sort of rectification. 
How do you value this 20 year old car Mark, when you have it back in reasonable working order?

[Moz18]

Yes I guess magnet. For me it’s all about learning, I’m getting into the mechanics side of things and these are great ways for me to learn! So far the car owes me less than £400! The car is in immaculate condition! 

[Magnet]

OK Mark, but repeating :- 

What value would you put on the car when it’s up and running properly? Take it it has a sensibly long current MOT. 

[Moz18]

Not sure not even thought that far ahead? Would probably keep it for myself

[Magnet]

Probably worth more for scrap/ breaking than the cost to rectify the issue. 
If you are not thinking that far ahead, then you certainly aren’t thinking about the whole issue from a logical point of view 

[Moz18]

Right…

Audi s4 4.2 v8, 78k genuine miles with full Audi service history. Just under 11 months MOT. Why would this be worth more scrap when it could literally be just a case of replacing valves? Money isn’t an issue for me as I’ve already stated… FOR ME ITS LEARNING or did you miss that part? 

[Magnet]

Really no need to shout Mark - we don’t do that on here.
Your car, your decision, your logic. 
Look at it like this Mark, you know the full facts, and if you only share that information with us as you see fit, then it makes it very difficult for anyone to offer you logical advice.

Good luck with it. 

[cliffcoggin]

1 hour ago, Moz18 said:

Why would this be worth more scrap when it could literally be just a case of replacing valves? 

Because the timing chain/valve problem is the result of plain and simple neglect, so you can be sure it will not be the only bit of maintenance that has been neglected. The chances are that the rest of the engine is worn out. The car may look immaculate but it is is actually a broken down wreck.