Wishing I hadn't bought this... misfire and major issues

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Spacecowboy

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Hi

I bought an A4 saloon knowing the camchain tensioner was phooked. So set about replacing that and the cambelt at the same time. The cambelt was loose but the car still ran. Put a new belt, pullys and damper on plus the camchain tensioner and gave her a service and she fired right up.

However she does seem like she is misfiring especially at low revs. When driving she seems ok no misfire but perhaps slightly sluggish. Just not running right at all.

I dont know where to go with her next. VCDS is throwing up misfire codes and the cat gets red hot and the car smells. Help!
 
Sounds like you have unburnt fuel getting into the cat.
Could be a tooth out on the belt or chain tensioner not installed correctly.
Coilpacks are very prone to failure, there is a VAG coilpack replacement campaign running so worth checking with your main dealer to see if your car is covered.
 
As paul says, its either belt or chain, to be honest it sounds more like chain to me, having done the tensioners numerous times i know it can be tricky to get them dead right,can you send a pic of the chain and the marks?

Even now i still have fiddle around more than once to get cam timing right on the chains!
 
Does sound like unburnt fuel in the cat + the cat may now be damaged (melted) and clogged up restricting the exhaust gasses getting out.

something like this!
slide_17.jpg
 
Exactly, but no big deal just remove the cat, literally falls out, took mine out with no problems and power gain is very noticable plus the motor runs much smoother.
 
The chain was a bit of a struggle but went in ok with 16 links between as instructed. I'll find some pics.

The cambelt though when we put that on was almost half a tooth out i.e. behind the timing mark on the cover but not by a whole tooth. If we advanced it it would be almost half a tooth the other way. I read somewhere that that was part of the design to allow for stretch in the belt? I suppose the question is is it better to have it behind or in front of the mark? For clarity ive replaced the j tube and prv and pcv also and cleaned out as many pipes as I could. I might have to take the cat off to have a look.

Also, if I put my hand on the pipe which feeds the injectors I can feel it hammering. Is that normal?
 
I think your exhaust cam is out, very common, cant quite make it out as pic is blurred!
 
This is what you should have, see how the ex cam (left) is slightly ofset to inlet then count teeth.

A3 5949
 
So i should have the above but I actually have the reverse? I marked the cams themselves individually so that they went back in precisely the same orientation as they came out?
 
What cylinder are the misfire codes on? that'd be my first port of call. The chani looks right to me, if you rolled the ex cam back like the picture itd just move the offset back instead of forwards. The difference of not having 16 teeth is much more than yours looks. No corralation errors? or setpoint not reached?
 
You are 16 teeth but the chain is wrong on the ex cam hence the reason your cam belt mark is out slightly the contact point on ex cam is critical you need to compress the chain tensioner and move the chain left on the ex cam , study the pic and you will see what i mean,its all about where the link actually sits on the cam and its definately wrong , i have had same problem numerous times infact i did i thread on it somewhere.
 
Right i think I understand what you are saying now. In essence I need to rorate the ex cam clockwise which will bring it into play on the timing marks and where the connecting links are on the chain.

Would running a cam off timing cook the cat? I'll run vcds and show the results.
 
Yes because ex valves will be opening to soon and the gases are burning in the cat not in the cylinder, inlet is not as critical but ex is.
 
Ok cheers. Morw shots above hopefully clearer. Looks like i best unbutton the lot then...

Cam I just compress the tensioner and turn the cam? Would I need to slip the cam belt off too? Just trying to visulaise how to right this wrong.

Let me know from the pics if the ex cam jumped a tooth and I simply put it back together where I started with my incorrect datum point
 
Cant tell from pic due to the angle, can you post a new scan? The link in the chain on the ex cam sits back 1 tooth, its the pin through thr link you go by, look at pic i put up and you can see the in cam link mark is 12 o clk but ex is slighty back from 12.

Its a tricky game to get right but you will know when its right because the cam belt mark will sit bang on.
 
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Move cam timing to marks if its half out then your chain is wrong.

Im near matlock derbyshire if your not far away i can come and help?
 
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Im in Worcester. Not huge miles away but I would happily pay your fuel and beer money to get this right!
 
Just realised actually you are couple hours away. Shame.

Could you give me a bit of a step by step i could have a go please?
 
20160813 122330

Sorry for the delay. Here is the latest scan. The MAF is just because I'd disconnected it whilst running to see if it made a difference.
 
As i said ex cam is out, those fault codes are exactly what you get.


The G83 sensor is in the bottom hose near rad ,it switches the fan on, could be faulty or just needs connections cleaning.
 
Last edited:
Ok so how best to remedy? Bearing in mind the crank marks lined up just the cam shaft was behind its mark? Do i compress the chain tensioner, take the rension off the cambelt and slip thr belt off, rotate the ex cam clockwise to line up the marks and put it all together again?
 
Spacecowboy said:
Anyone please?
Click to expand...
Undo the cam belt tensioner etc and take the timing belt off, then you can slacken off the exhaust cam carriers, you should be able to put the chain in the correct position without disturbing the tensioner but if you have the tool to compress it, use it.
Once you have corrected the cam timing then tackle the cam belt, the best way is to set the cam almost one tooth to the right of the mark on the rocker cover then once you set the cam belt tensioner it will pull the cam back to the correct position.
 
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QuattroCalum said:
Undo the cam belt tensioner etc and take the timing belt off, then you can slacken off the exhaust cam carriers, you should be able to put the chain in the correct position without disturbing the tensioner but if you have the tool to compress it, use it.
Once you have corrected the cam timing then tackle the cam belt, the best way is to set the cam almost one tooth to the right of the mark on the rocker cover then once you set the cam belt tensioner it will pull the cam back to the correct position.
Click to expand...

Quattrocallum just a thought. Given how youve said to bring cam timkng marks back into line i.e. set it slightly forward then as the tensioner takes up play it will bring it back in line is there a chance that just doing this will solve the issue? Rather than it being outright the position of the cam on the chain? Tackling this tomorrow hopefully with a mate so any help appreciated.
 
QuattroCalum said:
Wondering and hoping you got this sorted out today?
Click to expand...
No unfortunately mate didnt make it over so still stuck on this.

To answer your question cambelt did not line up on the cam makings but did on the crank I believe. I'm thinking Im in one of the following spaces:

1) The marks will actually line up if the belt is set just ahead of its cam mark then tensioned as you say which then brings it back into play in which case the cams are right (but could ****** up crank timing?); or

2) The ex cam does need rotating one tooth so slip the cambelt off and do that then put the cambelt back on;

3) As per 2 above but the in cam is also wrong and not in sync. I need to know what they look like statically times I guess.

To statically and mechanically set cam timing then is it just the notches in the end that need to line up with the arrow on the cam caps? Noting the correct chain position of course?
 
QuattroCalum said:
Don't leave us hanging, let us know if you get it fixed???
Click to expand...
Lol getting there. Dazz came down yesterday as promised and confirmed what I thought - the cam had slipped a tooth and was out of time. So he righted that wrong (top bloke) and we made surw we had 16 links. However the new cambelt kit that had been fitted had actually failed. The damper had siezed up so we couldn't finish up the job. I've exchanged it for a new kit today so just need to fit that then button it all up. Will let you all know how I get on but we were lucky we had to go back in there to find the dodgy new parts.

Massive thanks again to Dazz. Couldnt have done it without him
 
Couple of quick questions before I get on with this later:

1) should I replace the tensioner stud that comes with the new kit? If so is it just a case of locking nuts together to remove and install. 20nm (?) with thread lock or no?

2) is the correct gap between damper and tensioner 4mm or 7mm? Ive seen both numbers quoted
 
I would replace the stud unless you did it with the first kit and yes if you don't have a stud remover then just use 2 nuts.


As for the 4mm gap ,that's only on diesels as far as I'm aware on petrols you adjust the pulley how I showed you using the 2 small holes in the tensioner wheel to swing tensioner till you get the tension then you pull the pin on the damper.
 
Darran said:
I would replace the stud unless you did it with the first kit and yes if you don't have a stud remover then just use 2 nuts.


As for the 4mm gap ,that's only on diesels as far as I'm aware on petrols you adjust the pulley how I showed you using the 2 small holes in the tensioner wheel to swing tensioner till you get the tension then you pull the pin on the damper.
Click to expand...
Hi thanks. So no preset gap between the damper pin and tensioner - got it.

With regards to the stud, do i use thread lock or just tighten to 20nm
 
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