Timing (chain) tweaked yesterday, and all went well.

I realised afterwards that my concern about creating more slack on the tensioner side for the tensioner to deal with was nonsense.

There's no change in the tension anywhere in the system, because everything is the same as it was before, just the cam sprocket moved round a little relative to its shaft (to give the correct correlation with crankshaft).

There is a VCDS adaptation for adjusting something post-chain change, but I'm not sure that's essential. If anyone knows what benefit that might give, please let me know ( @stigma ?).

Seems more eager on the throttle from low revs, which was the issue - as well as the recurring elongation fault codes.

Needs the usual driver to comment, as she hasn't driven it yet. It will be interesting to see if there's any economy improvement too.

Edited 5 April5 Apr by Breezy_Pete

Happy Easter @Breezy_Pete

What do you mean with tweaked?

The value in VCDS (adjustment pre/post chain replacement) does not really do anything as far as i could detect.

Using ODIS, this option is not available as a part of the official rebuild procedure as well. It's more of a cleanup value/registry then something the ECU using for correlated live data.

There is no real variable timing on the CBZA/CBZA because they lack variable intake and/or exhaust phasers.

The only timing is when you align the cams with the camsprocket while the piston and cams are in the correct position.

You can set timing marks to see if your camsprocket has moved in relation the camshaft (marking the bolt and sprocket) itself but that's basically it. If it's off by by -5 ~ 5 degrees, your ECU can adjust for this by advancing or pulling timing.

If you think your camshaft timing is off, there could be a case for a jumped tooth. Only other condition is that the camshaft bolt lost grip and allowed your camshaft to move out of time.

Both instances would instantly be noticable with rough idle, misfires, increased consumption and loss of power....or worse, depending on how much it was able to move.

Edited 5 April5 Apr by stigma

By tweaked, I mean I locked crank and cam and then reset the cam sprocket in the correct place. Due to chain elongation, the correlation was off by a reported 5.8 degrees or something. See top of page 4 for vcds fault report.

Much easier than replacing whole chain, sprockets etc.

Also has hopefully cured a small oil leak from plastic top chain cover.

Edited 5 April5 Apr by Breezy_Pete

Perhaps i am missing something, it has been a moment since i did this one.

Does the camsprocket have an alignement dowl or slot to meet up with the camsfhaft?

In otherwords, can the sprocket move independently from the shaft?
If it does not, then locking the crankshaft and camshaft does not do anything practical, other then you have the reference mark on the sprocket pointing at certain position.

This is applies to the chain and sprocket for the oil pump as well.
You can try to align them but there is no timing involved.

I think i need to elaborate a bit on this specific issue.

If your engine did indeed jump timing by ways of the cold start "death rattle", resetting the cam gear is a bandaid.

All your components that keep your timing in check, wear out on each other.

• Timing chainValve timing.pdfTiming.pdf

• Camsprocket

• Chains guides

• Crank gear

• Chain tensioner

The main purpose of the tensioner is to compensate slack over time.

This means, that when (all) components have worn down to the point that chain tensioner can not compensate, you need to replace all hardware as mentioned above.

Again, in this engine, the only thing keeping your timing in check, is the tension on the chain. As soon as timing skip has occurred, mechanical components need to be replaced as a whole.

You just replace, for instance, the chain tensioner. This will do little for a permanent solution.

As this is an interference engine, your timing issue would have most likely created some other issues that require your attention.

This is why you HAVE to replace everything in unison.

Also as a side note, the bolt used to lock the camsprocket in place is a stretch bolt. This means it's a 1 time use bolt.

You are lucky it didn't break inside the camshaft.

EDIT:
I added the 2 steps that are all that set timing (see red circle). That is the only thing that sets timing. Everything else explained is what keeps timing.

Edited 5 April5 Apr by stigma

Lots of words there that I'll read later, but no, there is no dowel or fixed alignment between camshaft and sprocket, you just do up the (new) screw when you have everything correct.

I don't believe the chain ever jumped a tooth.

The tensioner was replaced 6 months back approx.

Edited 5 April5 Apr by Breezy_Pete

2 hours ago, Breezy_Pete said:

I don't believe the chain ever jumped a tooth.

The tensioner was replaced 6 months back approx.

So, your assumption here is that the camsprocket was able to move, seperate from the camshaft, based of the correlation message?

There so many concerns that, i stated a few times now, really require more then just realignment of the camsprocket, relative to the camshaft.

If this was the case, the chain would have been slack for a second, meaning the crankshaft was already spinning before the camshaft did which spells disaster for an interference engine.

What do you expect was responsible for the sprocket to move?

The bolt backing out of the sprocket is only a common issue on the 2.0 tsi. Most commonly on the intake phaser/cam gear side that's oil fed.

I hope everything purrs like a kitten again and the issues are resolved.

Edited 5 April5 Apr by stigma

1 minute ago, stigma said:

So, your assumption here is that the camsprocket was able to move, seperate from the camshaft

No! The chain elongation simply meant that the correlation between shafts was no longer correct.

If the driven (front facing) side of the chain gets a little longer, the cam becomes 'late' relative to crank position.

Adjusting cam sprocket alone can fix this.

Edited 5 April5 Apr by Breezy_Pete
Explanation

Main driver reports "best it's ever driven".

Seems very happy with the improvement, as am I.

I think your doubts @stigma my be partly due to not yet having understood completely.

That's great news!

Indeed, i didn't go thru the entire thread. I predominantly judge it from a mechanical perspective.

I am still unsure how removing "excessive" slack by realigning the sprocket has had 0 adverse effects.

Either it was out of time, or it was not.

Chain stretch is microns work. Realignment is mm work.

Anyhoe, glad it worked out

Edited 6 April6 Apr by stigma

It's not removing excessive slack. It's simply compensating for stretch. The slack is still being taken up by the tensioner

There was no excessive slack. Think of it as crank in locked, pushed against pin position, with cam slightly 'late' initially, due to chain being slightly longer.

Then free the cam by loosening sprocket screw, and rotating cam forward to its correct position (where the cam lock screw will fit nicely), while sprocket stays where it is, with tension on driven side of chain.

The tension everywhere is the same as before, but thanks to the infinite adjustability of the cam sprocket, engine is now timed correctly.

Edited 6 April6 Apr by Breezy_Pete
Clarity

It's not that i don't understand what you did, it's my inability to explain and get my view across on why this is not a good thing in the long run, from a mechanical perspective.

It doesn't matter. Good job non the less!

On to the next job 😉

Edited 6 April6 Apr by stigma
Typo

Thanks.

I realise it isn't the very best approach, but it cost me a lot less of my precious (I'm old!) time and effort.

I was happy to do this on this engine, because I know it may have other problems that would require possible major work or DIY complete replacement (that's often more economical in time and money in this country, not true everywhere).

I'm thinking there of a possible fire-ring headgasket leak which may be responsible for the coolant pressurising.

I did find my spare intercooler matrix to try, just in case it might be that instead, but haven't fitted that yet. I doubt it is this, but worth trying for the minimal effort at some time.

I managed to do the whole top chain cover off/on without draining coolant, by tying those hoses out towards expansion tank and removing the plastic clip from around them. That gave just enough space to move the sealant coated cover back into position without knocking it on anything and disturbing my neat lines of sealant. Must pop out and check if the oil leak seems to be gone after this morning's drive.

It would have been easier to clean off the old sealant if I had drained coolant and moved that lot all completely clear, and I could have used the locating pins from the timing pin kit if I had.

I'm writing most of this for the information and interest of anyone else reading who might contemplate doing the same, if they get the same fault code.

Other crucial thing is to remember that the crank locking pin, only locks it in one direction; you have to force the crank clockwise against it to be sure the crank is in the correct position. This can conveniently be done with a 12-point 18mm socket-plus ratchet handle, or ring spanner, on the crank bolt, ratchet strapped back to the wishbone, preventing reverse crank rotation while making adjustments up top.

This pic was taken before my partner made me realise that plastic hose bracket could be removed.

(It needs to slide towards the firewall 10mm to come off, there's a sneaky locating pin on it at the bottom which goes into the rubber 'hose grouper' thing).

Edited 6 April6 Apr by Breezy_Pete
Sp, goes not hoes!

And this pic was taken just before lunch. First time I've seen this output in a while 😁:

1 hour ago, Breezy_Pete said:

Thanks.

I realise it isn't the very best approach, but it cost me a lot less of my precious (I'm old!) time and effort.

I was happy to do this on this engine, because I know it may have other problems that would require possible major work or DIY complete replacement (that's often more economical in time and money in this country, not true everywhere).

I'm thinking there of a possible fire-ring headgasket leak which may be responsible for the coolant pressurising.

I did find my spare intercooler matrix to try, just in case it might be that instead, but haven't fitted that yet. I doubt it is this, but worth trying for the minimal effort at some time.

I managed to do the whole top chain cover off/on without draining coolant, by tying those hoses out towards expansion tank and removing the plastic clip from around them. That gave just enough space to move the sealant coated cover back into position without knocking it on anything and disturbing my neat lines of sealant. Must pop out and check if the oil leak seems to be gone after this morning's drive.

It would have been easier to clean off the old sealant if I had drained coolant and moved that lot all completely clear, and I could have used the locating pins from the timing pin kit if I had.

I'm writing most of this for the information and interest of anyone else reading who might contemplate doing the same, if they get the same fault code.

Other crucial thing is to remember that the crank locking pin, only locks it in one direction; you have to force the crank clockwise against it to be sure the crank is in the correct position. This can conveniently be done with a 12-point 18mm socket-plus ratchet handle, or ring spanner, on the crank bolt, ratchet strapped back to the wishbone, preventing reverse crank rotation while making adjustments up top.

Nice write-up.

I'd like to add that you need turn the crank in it's rotational direction (clockwise) as it's designed to only turn one way.

2nd thing i would like to add is to make sure you locked the crankshaft in it's correct position in relation to the camshaft position meaning, the camshaft needs to be in TDP. You are able to be on the wrong stroke and lock the crankshaft in the correct position, but in the wrong position for the camshaft. Double check your work that you can lock both in the same position to save yourself from doing double the work 🙂

Edited 6 April6 Apr by stigma

Had to borrow the Roomy to nip up to the Post Office earlier, and I refuelled it while I was out and about. It took 43 litres; 430 miles on the trip meter.

Definitely better mpg (that is ~45mpg) following the cam angle correction. No idea what a 1.2TSI Roomster is supposed to do?

Previously, it wasn't going much further than that on 50 litres.

So if i convert your metric and British imperial units and i round up to 700km's for a full tank of gasoline? That's a thirsty engine.

Keeping it metric, the fabia is

1136kg's wet weight

Tuned to 143hp and 245Nm peak torque.

Gas tank is 43L.

Average comes around tot 1L to 100km.

Converting that back to imperial numbers:

Average consumption, based on ~ 90% freeway @60mph is 56 miles per gallon.

That's the kind of consumption I'd like to see, but with worse aero and some more weight (I guess?) Roomster is going to struggle to match Fabia, I expect

Edited 17 April17 Apr by Breezy_Pete

I see the Roomster has a gas tank capacity of 55 liters and wet is 1221kg.

Judging just based on the exterior, i doubt that the cw (Cd) value is that much higher then the Fabia estate.

As i mentioned before, all the engine mechanics need to be top notch for it to operate at it's best.

Use VCDS to check your engine balance:

Fuel pressure

Lambo

MAP

Etc etc.

These engine suffer from vacuum leaks, pcv and oil separator issues.

Then ofcourse, there are the standard VAG issues like carbon intake fouling, exhaust leaks, thermostat housing leakage, water pump failure, general gasket failures etc etc.

My best guess is, you are suffering from vacuum leas from the brake booster side or perhaps a faulty control valve from the EVAP system.

Does the car run a little rough at idle and/or cold starts, but normal under load?

If so, definitely a vacuum leak or intake fouling.

14 minutes ago, stigma said:

carbon intake fouling

Definitely has some of that, I had a look when the intake manifold was off for clearing of that completely blocked 'secret' PCV valve. Very hard to clean ports/valve backs in-situ I thought; so didn't even attempt.

I don't think there are any other significant problems, it runs very smoothly and inaudibly at idle, hard to tell whether it is running from driver's seat, without looking at rpm.

Turbo is known to have significant play in the actuator linkage (discussed earlier somewhere upthread), but I can only see that affecting transient conditions.

If I remember, I'll research Roomster 1.2 TSI real world consumption on spritmonitor.de over the weekend, for crowd sourced baseline.

In completely different news, who knows what this tool combination does?

(21mm socket normally for spark plugs, with important hex flats, and 7mm hex key shortened by about 25mm earlier this evening to fit under an obstruction).

Spritmonitor is saying 40mpg is about average, which sounds believable, given the age of most of these cars.