NeilTM

Yes, perfectly adequate power and the engine itself ran fine, and quietly - right up until we left it with Mr Clutch ;-) Only needs one weak link in a chain to spoilt the entire chain. And sometimes the entire chain is the weak link it seems. Far too many horrific weak links in cars these daze IMO.

Thanks for checking Damo. We read about a Ford Transit that this was an issue with: https://fordtransit.org/forum/viewtopic.php?f=5&t=105454&c=1 But in general it seems to be only a few engines where a worn TC tensioner can slacken the chain sufficiently to jump a tooth if turned backwards. The 1.2 engine in the Fabia is listed here as one of the worst 7 car engines for reliability because of the timing chain failing: https://drivemag.com/news/seven-engines-to-avoid-when-buying-second-hand-cars Which whatever the shortcomings of that particular survey might be is at least suggestive that a generalist garage is likely to have encountered or at least heard about this problem, on what seems to be quite a popular car on the road, and should be aware of these risks. And here, https://www.thecarexpert.co.uk/most-reliable-engines/ and in other surveys VAG cars have the worst engine reliability ratings apart from MG Rover, but they're long gone now, so they, or more specifically the Audi part of VAG are the worst there is apparently, averaged over a makers entire range of engines, based on interrogating Warranty Direct's claims database, so obviously some good, some bad amongst that lot for any maker. VW themselves come ninth worst, but Skoda specifically isn't listed in that summary, not all cars are represented in that survey if the numbers of them insured with them are too low, not to have the potential to constitute an inadequate sample and skew the results. With BMW not that far behind with TC issues of their own, not least having to hike the entire engine out of a car to get to their troublesome TC! Only Mercedes seems to redeem the Germans at third best.

Gosh, yes, I hadn't appreciated that the tensioner was oil pressure activated, as opposed to a spring, but that makes perfect sense as a damped, essentially hydraulic mechanism you would want it to be, and a spring would not deliver. What this also surely points to is that a timing chain jump in normal use is far more likely, perhaps even only possible at start up, when the functioning of the tensioner has not yet been fed the oil under pressure it relies on to function properly, or as you say a sustained push may have evacuated it. A momentary rock backwards on stopping the engine would have no effect as the device would be fully primed, even if worn, but may perhaps then evacuate it, setting it up for potential failure to take up the chain slack at next start up just as you say. But then the all important Q is in what direction would the jump occur, and the answer surely has to be that if the engine is cranked on the starter and fires and runs normally, throwing out the starter dog as it revs up, then the only possible direction of jump in that sequence is to get ahead on the chain, and any jump occuring will therefore retard the ignition. If the starting sequence is interrupted or fails, and the engine doesn't fire and run normally, then the engine MAY be permitted to run back a little way. It may run back a lot I suppose if there is the sort of kick back as could be experienced with a starting handle, where if you had your thumb wrapped round the handle and it kicked back, where the firing before TDC pushed the engine violently backwards, you could break your thumb as opposed to the handle flying out of your hand. A good question might be to ask whether such events are still possible with computer controlled spark and fuel injections though, I don't know. So maybe the question as to whether backward rotation of the engine at a failed start up might be sufficient to permit the engine a backward rotation sufficient to provoke a jump in the direction of advancing the timing, still relies on a difference of degree of backward rotation between a slighter (at start up), or greater, and more sustained (during dismantling) turn backwards? Hence my separate Q on this forum made in the hope of discovering if there was any consistency and in what direction the jump occurred when it happened at start up. I know that that car has always started reliably as most modern cars usually do, so it seems unlikely that there would have been a fluffed or failed sequence when my son started the car to drive it the approx 3.5 miles to the garage. But if it had jumped then it surely would not have run and idled normally enough, if at all, while the ECU learned new settings for idle and running, as my other daughter's fiesta had to do only the other day when it lost its VRAM running settings, and I sat and ran it to normal temp from cold, then left it alone for an hour or so before it would finally fast idle, before settling back down to normal on a short run. If this is so then this might provide additional reasons to those already stated why the jump did not occur before the car arrived at Mr Clutch as such running would have been inescapably memorable. The other stretch on that scenario would be to have to ask if it could really take as much as 8 or 9 miles for the ECU to suss the 20degree jump and put on the EML. But 5 to 6 miles at least it must have taken, so........? They now want to say that the broken clutch caused the jump, so I asked them 'how precisely'. At most the partially disengaging dragging clutch, which was insufficient to 'creep' the car forward at all, would simply add to the load on the crankshaft pulley, but unlike a piston under compression or the spring tension from the valve springs would not of itself provide any backwards impetus surely? Maybe even act as a damper on such movement?

Yes, I think I made this point myself. But clearly it must be a question of the degree of backward turn, if these routine events, at least every time an engine is stopped do not in fact result in a jump, then a clutch replacement does the trick. It seems perfectly possible that had the clutch needed replacing 30,000 miles ago, that this jump might have occurred during clutch replacement then, and by the same token that it might not have occurred for another 30,000 from now, if the clutch work was done then. Nobody has that crystal ball, and such speculation is unprovable and irrelevant. I seem to recall a similar issue with some alternators not liking to be turned backwards, but again that presumably refers to being turned back more than the little rock produced by cylinder compression being lost that way as you describe. Mr Clutch read my final much stronger reply to their brush off sent late last night and they replied early this morning saying that they were giving this to the local area manager to look at and get back to me asap, so hopefully they might be starting to take this seriously.

Indeed, a fascinating tale, also containing a little pearl of information about where to find VW tech info: https://erwin.volkswagen.de/erwin/showHome.do Private individuals can subscribe. Minimum subscription is for one hour access, so an expensive sounding pearl hire business. (the online info becomes inaccessible when the hire period expires) Anyone here already have access who could tell me if ErWin might have clutch replacement procedure information that might contain a warning about not allowing the engine to rotate backwards? late 2005 Fabia 1.2 BME engine.

Thanks Wino, I do appreciate everyone trying to watch my reckless back, LOL Nothing 'official' as such as yet, but if I have to find something then I will, if it is only the testimony of experienced mechanics undertaking this work, and here is an example of that I found online, http://www.bba-reman.com/forums/Topic108918.aspx?PageIndex=2 where the respondent informing of this backward rotation situation, and others in that thread reveal they are professional mechanics. I know that my local VAG independent would be happy to write testimony to the fact that this happens, and probably be prepared to share their procedure for ensuring that it doesn't, and even the mechanic who replaced the clutch did not contest that this could happen when I put it to him, nor their head office, only that he would not have made this error.

Now that sounds like a tale worth repeating!? Reminds me that when I took my 16yo Fiat Doblo with 150,000 miles on the clock in to a so far very impressive independent Fiat specialist, he pointed out to me that my aux belt was original! And sure enough this otherwise meticulously dealer serviced, single owner vehicle had not had this changed for the simple reason it never appeared on any service schedule to change it! Tell me VW made the same omission and that is why its failure to specify its change resulted in the demise of the engine?

You could well be right, but as my brother pointed out "With the defendant judging the case, I think the verdict is inevitable. I guess that's why we need courts." They don't teach logic in schools for a reason. While my logic might defeat Mr Clutch to understand it, the courts are a different prospect.

Thanks Wino, and others above. IF the only way the timing could jump in the direction of ADVANCE is by backward rotation, I don't see that it matters to establish at precisely what point or in what way this happened during the clutch work, and we already have demonstrated that getting honesty out of them is unlikely, so your questions would just get us hopelessly bogged down in fresh opportunity for their further obfuscation, without doing anything to reinforce the central point which I now made that the engine must have been rotated backwards for the TC to end up where it has, and their vague woolly account of how that could have happened as due to the severity of the clutch failure which they are simply egging for dramatic effect, and I am countering by demanding they get specific about how a broken clutch can turn an engine backwards as I don't see how it could. You are quite right about the effort and stress to get them to pay for this repair, but its already been largely expended, I've proved my case I think such that a court would accept my explanation and proofs over their vaguenesses and provably false narratives. The only way I could have avoided it would have been to accept being lied to and robbed from the outset, so I'm choosing my own source of misery since this way there is at least a chance that I might force them to take responsibility, if only for culpably failing to notify us of an additional engine running fault they are now claiming they were aware of before they did the clutch. This should get them their RAC accreditation taken off them as had they informed us, in accordance with those RAC standards as they should, of additional issues we would have investigated them, or had them investigate them first, and made a decision to scrap the car at that point as it would not have seemed worth spending a total of £618 with them on two major jobs on a car of this age, mileage and market value. We were entitled to the full picture they claim they knew existed to be fully discovered before doing only one of the jobs presenting themselves at that point, which makes no sense to ignore, but of which we were unaware. Instead, we got lied to in one of the two ways I have outlined, which itself is strongly suggestive of trying to cover up a mistake they made which triggered the TC jump. And there is seemingly no other contender now for the jump than the clutch work. I shall send an already completed draft reply to their brush off email to them now, so that it is waiting for them first thing Mon am inviting them to reconsider undertaking the full kit replacement TC & T without charge in another of their workshops, in light of me busting them basically, giving them until one working day before the appointment I shall be making to get the work done by our trusted local VAG independent, after which they will get the full bill, and I will take legal action if it isn't paid.

I realized that my own brother who used to in his own words "design the components and systems that go into a vehicle", his specialism being the electronics and programming side, might have the answers I was seeking as to whether battery disconnection could extinguish the EML even if the codes persisted, and he has come up trumps and with a lovely bonus that he feels proves how the jump occurred. This is what he wrote: "Having worked with the VW-Audi group, I can assure you that the standard functionality required of any ECU on their vehicles requires DTCs to be held in non-volatile EEPROM or 'E-squared' as it is often called. This requirement is, to the best of my knowledge, industry-wide and has been so for over 20 years now, so the Mr Clutch people really should know better! The Engine Management light is then controlled by the instrument panel after it is signalled to do so over the CAN bus (the instrument panel does not have to 'remember' the status of the light itself.)" EEPROM: Electrically Eraseable Programmable Read Only Memory I still wasn't entirely sure that what applied to the codes also invariably applied to the presence of the EML but he assures me that in these circumstances - of a permanent fault such as the timing chain jump it does: "A fault such as a 20° timing chain jump is not intermittent, so once detected by the engine ECU, would be permanent. The EML would be on continuously - end of story. Intermittent faults are recorded with DTCs that are flagged as intermittent and an incidence count is maintained for those faults and the EML could come and go or take some time before it is lit - but this fault isn't and cannot be intermittent, so that cannot apply here." He further stated: "I know there was a requirement, (in the specs the car manufacturer gives to the developers), to remember DTCs through power cycles and that includes units that were not supplied with a permanent battery live. (that's the Fabia as Wino pointed out) The only practical way to do this is to store them in some form of non-volatile memory, so that is what is routinely done. To the best of my knowledge this has been a requirement in every car manufacturer's specs on this planet for over 20 years." I really hope anyone and everyone struggling with being mislead over the permanence or transience of codes and EMLs can find their way to read this as it lays a lot of myths to rest and introduces certainty into a picture where ignorance may otherwise be exploited. So I now have categorical proof that their account could not have happened as they said. Either they lied about the EML being on before work commenced, or they lied about how it came to be off after the work, as the only way it could not have remained on was if they deleted the codes, either of which is a serious untruth amounting to deliberate fraud designed to evade any responsibility for this event and put it entirely on the customer. But it gets even better, (or worse for them) if you ask what type of event is necessary to cause a timing chain to jump, such that the direction of the error, as in this case is towards the timing becoming ADVANCED? My brother again: "the direction in which the 20° jump has happened: Given that the motive force for such a slip can only come from the crankshaft, the camshaft being the load, so if the valve timing is now 20° advanced, that proves it can only have happened by turning the engine backwards and how would have that happened (in this instance) other than during clutch replacement?" I had to sit down with pen and paper to visualise this, whereas a child's toy set of sprockets and chains might have helped considerably to model this, but he is right, the crankshaft has to end ahead of the game with the camshaft, with the motive force being engine rotating clockwise, and vice versa if moving counter clockwise by the same principle. Remember the camshaft is a significant load, it is constantly opening and closing valves against strong springs, so it is a significant resistive force opposing the crankshaft turning it. With the crankshaft jumping ahead of the camshaft through the slackness of the chain, the camshaft becomes behind in sequence to the crankshaft, ie its valve work is RETARDED. But if the motive force of the crankshaft is counterclockwise, the engine being turned backwards, the same principle determines that the jump will occur in the opposite direction, and ADVANCE the timing. The timing on our car is now ADVANCED, therefore the jump was produced by the engine being turned backwards. And how can that happen? By turning it backwards during clutch replacement work! And we don't think it is possible to visualise a scenario where a broken clutch release mechanism can cause the engine to move backwards as they now claim. Are we wrong?

Where people have reported incidents of timing chain jump, on any vehicle, whether at start up, or after cranking an engine, or during clutch replacement, has anyone recorded which direction the jump occurred in? Did it leave the timing advanced or retarded? Please be clear about the precise circumstance in which the jump occurred if able to report whether the timing became advanced or retarded. Thank you.

I am reproducing below the essentials of the Mr Clutch response which took them exactly the promised fortnight to come up with. Right arrowed is their text, with my comments and questions inserted: On 12 Dec 2019 at 11:33, Customer Services | Mr Clutch wrote: > Dear Mr Taylor, > > I am writing to you further to your email dated 27th November 2019. > > We would like to respond as follows. > > The sequence of events : > > Your vehicle came to us on the 13th November 2019 for diagnosis and after > a very quick test in the car park without moving the vehicle we could > ascertain that the clutch had catastrophically failed and was > undriveable. > That is egging it a bit as we drove the car to them. The clutch was working but dragging - not fully disengaging and as we thought, they stated that it was a broken clutch release mechanism. ......... > It was noted that there was an EML light on and the engine was slightly > rough in running before we stripped the vehicle. This was first mentioned only after we had diagnosed the timing chain jump and reported this to them. Only then did they change the narrative to claim that the light was on when they took the car into their workshop. But when I asked why it was not still on upon receipt of the car after the clutch work, they falsely claimed that disconnecting the battery lost the codes. This we tested by disconnecting the battery for a whole day, whereas their work took 5 hours. The EML and codes were still there upon re-connection without re-starting the engine. Therefore either they lied about the EML being on before their work, or they lied about deliberately deleting the codes since that would have been the only way they would have disappeared and the EML extinguished. > However, due to the severity of the clutch failure we presumed that > the two were linked in the same way. The EML light was on because the clutch was broken? How does that work? > After replacing the clutch the > engine was smooth on the idle, however did lack performance when > tested. No light was on at this stage and all work we carried out was > rechecked. > So after demonstratig to them that this narrative doesn't stand up - couldn't have happened - they simply repeat it, merely omitting the bogus battery disconection explanation given at the time! They are not coming up with a possible narrative. I also reported their stupid forced revving beyond the ECU imposed 3,000rpm limit, but they've just blanked that. > The car was collected from our Autocentres and advised suspected catalytic > converter blocked, due to symptoms we had experienced, had we plugged in a > diagnostic machine at this stage and retrieved the codes you retrieved out > of the vehicle then it would have pointed to the timing chain and not the > catalytic converter and we would have advised accordingly. > Which begs the Q as to why they didn't do this, and do it before the clutch work, since it is trivial to do and takes a few minutes at most, yet they apparently had time to rev the engine and repeatedly force it with a 'pop' to go beyond the 3,000rpm limit after the clutch had been changed. Only after the clutch work did they show this much interest in the engine running. > With reference to the technician concerned he is a long standing employee > of many years with us and is not a liar, he is part of our National > Support Team and is held in high regard. > And Popes are infallible too. I caught him in a lie, so why not use the word, when it is demonstrable? They on the other hand have implicitly claimed that we were lying by claiming a prior engine management light that never was, but still fail to provide an explanation when challenged to account for it disappearing during the clutch work. > To reiterate the information the poor running was due to the clutch > breaking up and not any other problem, we refute causing the problem of > the timing chain failure and could have been caused due to the severity of > the clutch failure. > Apart from this not being a grammatical sentence, but I'm assuming a missing 'it' between 'and' and 'could', can anyone tell me if a broken clutch release mechanism, preventing full disengagement of the clutch, such that the gears crunched when getting into first or reverse could cause the timing chain to jump? Has anyone heard of this happening? The thought that this might be possible occurred to me before it apparently occurred to them, since they have taken until now to relay this possibility. But is it a possibility, in which case what is that scenario - how does that work? If anyone has ever hand cranked an engine with a spanner, or a starting handle for that matter, they have probably noticed that if this hand cranking is ceased while a piston is approaching TDC on the compression stroke, that the pressure built up might result in a slight backward turn of the engine. This can also occur if the starter motor is released prior to successful firing and running of the engine can it not? Is this slight backward rotation what can cause the TC tensioner to 'unload' its tension, allowing for a then slack chain to jump? I am assuming that since this particular car never had any starting issues, always firing and running straight away, that this scenario simply never occurred to allow for a TC jump? I would also like to know if there are any professional experts out there that anyone knows of who might be able to give a definitive opinion on this Q such that a court would take them as an expert witness? Who could I turn to for not merely a legal opinion, but an opinion of a qualified technician or engineer, or a technical document? If they are trying to fudge the issues of the codes, as opposed to just being too stupid to understand what they are talking about, then it would be good to have an authoritative reference about the non volatility of these codes. By miserable coincidence, the other day my son in law used his fiesta as a torch with which to light up the front of the house putting up xmas lights, then forgot to turn the headlights off. The resultant voltage crash lost the apparently volatile (VRAM) engine running settings, such that when I got the car started after re-charging the battery it wouldn't idle. It eventually re-learned its settings and was OK again. But I'm still assuming, and our experiment confirmed that this does not apply to engine sensor codes such as camshaft etc? > With regards to the EMC light coming on, it can vary how quickly the light > comes on and there is no set time or mileage. > Yes, or at least that's what I've heard, but irrelevant. What I asked them to account for was the *disappearance* of the EML during the clutch work. > Taking the above into account we are more than happy to carry out the > repair for you but we cannot do it free of charge. > Now that it seems we are potentially going to have to take them to the small claims court to get a bill for fixing this elsewhere paid, I need to have expert testimony that I have a good case on the central points above. I think the failure of their narrative, and simply repeating it without offering any explanation in place of the one I demonstrated to be false, suggests that my exposure of that falseness is not possible to get round without liability, if only because being caught in a lie destroys the probability of the jump occuring before the car landed on their forecourt as they claim, and makes it much more probable that it occurred during the clutch work which they simply refuse to entertain the possibility of. Why lie about something that wasn't their fault? But also their failure to notify of the engine fault revealed supposedly by the EML being on before commencing the clutch work? Can a broken clutch release mechanism put up a code? Not notifying us of other issues before undertaking major work contravenes their RAC approved garages accreditation, but their chocolate fireguard remedy involves binding adjudication, a process that apparently can take up to 3 months, so nothing to do with getting a needed car back on the road in a timely way, and so unlikely to ever be invoked much I imagine. Any information and advice on the above would be much appreciated.

Battery disconnected all day. Re-connected, codes and EML still there. Dealing with a BS merchant. No time to deal with this on Monday, so will tackle manager Tuesday.

My son is testing the possibility that the codes were erased by the battery being disconnected, by doing the same, and we'll know the answer later today. My son wrote to me: "I .... asked him to explain the issue where he described the engine struggling to rev above 3000rpm though he said could do after trying for a little while at which point it gave a "pop" and would then rev higher (not our experience). At no point in that conversation was EML mentioned by either of us." This in itself is worrying, as it seemed obvious to both of us that a rev limiter bang on the round figure 3000 mark every time would be an ECU limit introduced, so trying and apparently succeeding to make it rev higher with a 'pop' sounds alarming and irresponsible, and makes me wonder if any damage might have been done by doing this? They also said to my son they would have to read the 'historic codes' when it came back in for assessment, logically thereby also claiming they never read them when the engine management light was on, which they never mentioned at all to my son, or reported it having been at any time whatsoever until I went in with the car, informing me only then that it was on when they first started the car.

Just wanted to bump this one of my original questions: So my first Q is how long is it likely before the ECU would recognise the persistence of a fault, as opposed to a transient, before logging trouble codes and putting on the engine management light? The delay experienced was a 2 mile journey home, plus approx 1.5 miles into a trip the next day before it came on? Is this a possible delay? Might actually have been 4.5 to 5 miles. The rough running and 3,000rpm rev limiting were certainly there from picking up the car.

This post escaped before I could edit this out having learned from reading the Haynes manual that the sump has to come off as part of the quite considerable work involved in getting at the timing chain. Based on the look of the job, the quote of itself might be reasonable, even for a specialist used to doing this, but this of itself is not the issue. If Mr Clutch don't come through, the VAG independent specialists I know and trust, but who wanted £388 for the clutch, I might get to quote for the work, but wouldn't expect it to be cheaper necessarily.

Sorry, some key combo keeps sending my replies before I'm ready to send them. Yes the clutch work was 'cheap', but then they were billing themselves as clutch specialists - 'Mr Clutch', and they seemed to have good reviews. There was a £10 voucher included, and we got other quotes under £300. It subsequently became more apparent that they were generalists (as well?). Tough as it might be for a struggling lone generalist mechanic to get caught out unexpectedly by this engines nasty trick of jumping the timing chain if not proceeding correctly, they would none the less be responsible for correcting their mistake, but I can't accept ignorance of this scenario from an experienced clutch specialist as the guy in question was insisting he was. I can of course accept an honest mistake, but he absolutely insists this didn't happen, and couldn't have happened because he knows what he is doing. It must be nice to be incapable of ever screwing up, but there we are, LOL. Code clearing is my focus now. Can his narrative still stand up? To get a car into a workshop that throws a wildcard like this must be challenging to know how to deal with for the garage as well, which will naturally want to minimise, or entirely disown liability. I would be naive not to properly explore the possibilities of back side covering strategies coming into play here. Sepulchraves suggestion of paying for the parts if they agree to the labour is what I'm favouring so far unless their code clearing narrative falls down.

Thanks Wino, I could do with as much certainty as possible over whether merely disconnecting the battery in the course of the however many hours out of the day they worked on the clutch would clear the codes as the mechanic claimed. Isn't there an issue of capacitors discharging, or of needing to employ some other procedure such as turning the ignition on and off three times (we read somewhere) for the codes to be cleared that way? This now seems critical to establish, as it now occurs to me that they may have deliberately cleared the codes and with them the engine management light in order to be able to get the customer to take the vehicle away after paying the bill, whereas with the light still on, wouldn't some or most customers be reluctant to drive the vehicle at all? They did report rough running, and revs limited to 3,000 and offered to book it in at first available opportunity to be looked at, and this appointment we ultimately kept, after having meanwhile establishing the cause, and reporting this to them. This is absolutely critical to establish, because if the codes disappearing incidentally, non intentionally, because of the legitimate battery disconnection for the clutch work could not happen, their narrative collapses, and the basis of trust in them is destroyed. I am not angry by the way sepulchrave, more in shock and utterly dismayed that this nightmare could have unfolded, trying to be calm and rational and explore all possibilities. I want to discover the truth of what happened if possible. The mechanic seemed to know what he was talking about, and certainly had all the answers, and unless the battery disconnection clearing the codes could not have happened, his narrative remains possible, whatever the probabilities might be. One possibility is a deliberate clearing of the codes and extinguishing the engine management light in order to minimise the alarm of the customer taking their car in for a broken clutch and receiving it back with a broken engine! He was still emphasising his favourite contender, a blocked cat, just before he discovered yesterday we were right about what the fault was. Answering other replies for brevity, (not my strong point!): Cheapness:

Yes, plus the fact that as sepulchrave says 'many' instances of chains jumping at start up have been reported also. All the more reason to do as you say and replace the parts. Although I would take issue with your penultimate sentence, as it should be a known issue to a specialist that this can happen on the basis of normal wear alone, despite not being a service item like timing belts, and why there are counterholders presumably? Which brings me to 'what parts'? Ebay has a bewildering choice of kits with different contents, and widely differing prices. Replacement cam and crank shaft sprockets seem to be most commonly included, apart from just the chain and tensioner, but not always. Included in the quote the garage gave was the cost of an engine oil and filter change, something I always do myself. Is this invariably needed? The garage will presumably want to source parts themselves. Is it possible to say a range within which a reasonable charge for parts might be expected to fall?

Good advice sepulchrave, thank you. It hadn't actually occurred to me that they might have deliberately damaged the engine, but now you come to mention it, the possibility seems no less unlikely than some of the other possibilities, such that the mechanic screwed up on this occasion and decided to cover his back with his boss, knowing it could not be proved, but I have been going the other way and trying to convince myself that it wasn't an accident either - something the mechanic vehemently denies, and this might be, just as he said, how they found the car. Now that you tell me that chains jumping at start up is a known occurrence, that changes the picture for me, leaving me just with the incredible timing of the mistiming. Which leaves me thinking that if I am supposed to swallow that, as it seems I must, because however unlikely, it might be true, then they equally should return that good faith by accepting that this is indeed what happened, at the point they went to start it to drive it into their workshop, and that therefore they were not making a reasonable assumption that we knew the EM light was on as an excuse for failing to inform us BEFORE they did the clutch work, any more than I would have been entitled to assume they must have triggered the chain jump by letting the engine move backwards, when a perhaps less likely possibility existed. Had they informed us before, not after they did the clutch work, and investigated that at that point, then we would not have gone ahead with either work at that point. For a decent firm, that ought to be enough as you say for them to shoulder the labour, and me to pay for the parts. We shall learn if they are a decent company on Monday.

Took car back to the garage which replaced the clutch. The most the mechanic would or could agree to, (he can't ask his boss because he's on holiday until Monday), was 'lets see what it is and I'll call you before doing any work'. I told him that I now knew for certain that the chain had jumped one notch, but he was still favouring a blocked cat. Obviously he must have chosen the easier option to check out first, and so he discovered that I was right. But he wasn't prepared to restore the chain to its proper position as I asked him to, as clearly (he said) the timing chain and tensioner had wear issues and whatever had caused it to jump (the minute they started the engine to move it into their workshop we are being asked to believe), would cause it to likely go again before long. Then there is the little matter of the £375 incentive not to simply restore the existing timing if you can charge for a new chain on the basis that the old one is not serviceable, which they cannot know, only guess to be the case, which in any case from the customer's pov is not an attractive option if indeed it might jump again at some point in normal use? The labour cost would be the same whether you changed the chain and tensioner or not. £375 for fitting new timing chain and tensioner, which on top of the new clutch at £243 comes to more than the thing is worth, and especially if you factor in the two new springs it needed for the MOT in Sept. If only it were possible to have hindsight earlier! So I said no way to the £375, went back in and he gave me the key and I said thank you and drove it home. No one is calling anyone a liar, but logically there are only 3 scenarios: 1. We are lying about what happened, or genuinely oblivious 2. He is lying about what happened, or genuinely oblivious 3. We are both right about what happened. For the last option to be true it is necessary to accept the possibility that between us delivering the car to their workshop with the engine running just fine, and no engine management light, and them starting it up to move it into their workshop, whereupon the light was on and the running rough, it was precisely at that point of starting it that the timing chain jumped a cog, before anyone touched it mechanically. This is what they are claiming, unless at some point they want to say we are lying or mistaken and we brought it in like that. He refused to speculate as to why or how such an unlikely thing happened, let alone AT PRECISELY THAT POINT, and that no way did the flywheel move backwards at any point during the clutch replacement. No fault codes or engine management light were present upon completion of the work because the battery had been disconnected for the work, and that clears the codes. How long does that take? I don't know. He had no answer as to why, when the engine management light came on they did not report it to us in order to make an informed choice about the combined costs of two major faults. He said that they presumed we knew the light was on. This comes close to implying we knew the car was crippled, rough running, radically down on power and rev limited, but for some reason decided we wanted just the clutch done anyway, but implicitly that maybe we hoped to con the garage into accepting liability for fixing this also. How else could you defend assuming that we knew the light was on, and therefore need not inform us of this? He is obviousely a knowledgeable and experienced mechanic, and knows all the get out of jail answers for sure. He knew that this jump would not have been possible with a new chain and tensioner, but then whether it was possible in the way it occurred according to them is another matter. I'm guessing it probably could, but what compared with either of the first two scenarios is the probability that it is as the garage claimed? What is the probability that we experienced both faults at much the same time, but thought we might be able to blame the timing jump on the mechanic, and thus only incur a clutch change bill and so lied about the engine management light not having been on when we took it in? This also presupposes prior knowledge or research on the possibility reported by some number of forum members that they experienced the chain jump occuring as a direct result of having the clutch changed. Or were we oblivious of the poor running because the dragging clutch making driving difficult sufficiently distracted on a journey in a 30mph zone masked the bad running and 3,000 rpm limiting? The answer to that has to be no on two grounds. The car was driven home at 70mph on a dual carriageway, and not driven again until taken the two miles to the garage. The top speed possible now at 3,000rpm is approx 53mph. And it is vanishingly unlikely that the revs did not hit 3,000 through the gears, even in the 30 limit as this requires geriatrically slow driving, and doubly unlikely if you are trying to avoid too many gear changes, and so letting it stay longer in the lower gears. Is it fair to say the latter scenario, of the clutch change procedure triggering the jump, which is a known and reported event is more probable? The odds on a jump occuring during engine cranking (even if ever heard of?) at the precise moment the mechanics first started it, seems like a rank outsider in the probability stakes to me? The balance of probabilities is what the small claims court would surely base their decision on a claim for correcting a fault not present when the car went into the garage for other work, but emerged from with the fault? Unless the guy with the full deck of get out of jail cards knows how to get out of that? Anyone? Maybe the manager might be prepared to go some way to put this situation right, or failing him the national Mr Clutch franchisers. We will have to see on Monday. Neil Taylor

18 crankshaft, 36 camshaft would certainly produce the 4 stroke cycle, and the crankshaft sprockets on ebay seem to have 18 teeth. I didn't know the numbers of teeth on the crank and cam shafts, so came up with 22.78 by different means as cited in my original post, so 20 degrees could easily account for an error in measuring the rise of the piston, as well as being the minimum error produceable by the chain jumping a tooth. 2 teeth would have been 40 degrees and surely impossible for an engine to start or run that far out. But this gives me the confirmation I sought, thank you. The camshaft locating tools are indeed 'authoritative'!, and I can take the laptop in if they want to argue the toss, but they should know this anyway. Wish me luck with them for tomorrow morning. Best wishes, Neil

Thanks Wino, that's very good of you. Just one quickie before early tomorrow, anyone: Am I likely to do any harm driving the 20 miles to the garage with the timing out by this much? 23degrees! Best wishes, Neil Taylor

Fabia 1.2 petrol 55 plate. BME engine. Firstly, a fond hello to Wino if he is still here, and who saved our daughter's Fabio from a fruitlessly expensive journey to the scrap yard for the mother of all obscure faults - a still mysterious break in the wiring in an inaccessible part of the cabin behind the dash next to the bulkhead, in a cableform - an absolutely brilliant piece of patient sleuthing and testing by Wino that undoubtedly avoided the inevitable ECU change the professionals we contacted would have needlessly inflicted on us to no purpose. 2.5 years of fault free motoring later, we arrive at another challenge to its future after having just had two broken springs replaced for the MOT, all too quickly followed by replacing a clutch as well for a broken release bearing, which we also correctly diagnosed. In a nutshell, the subject line is what we need answers to to be confident that the Mr Clutch franchise we employed to change the clutch were in fact responsible for failing to prevent a known hazard, namely the timing chain being caused to jump a couple of teeth, which we believe to be the case from our own investigations. A preliminary phone call to the garage met with denial of failure to secure the flywheel from moving backwards as it would upon tightening the clutch cover bolts if not first secured. This according to more than one forum post we found can cause the tensioner to 'unload' its tension, precipitating a jump of the timing chain of one or two teeth. Further confirmations that this is known to happen would be appreciated. No engine management light was on when the car went in for the clutch work, nor when it left for the 2 mile journey home, despite this being contradicted by the person we spoke to who said that he had done the work, and who claimed the light was on when we brought the car in, yet never informed us of this at any point. So my first Q is how long is it likely before the ECU would recognise the persistence of a fault, as opposed to a transient, before logging trouble codes and putting on the engine management light? The delay experienced was a 2 mile journey home, plus approx 1.5 miles into a trip the next day before it came on? Is this a possible delay? However the running and power was noticeably poor from picking up the car compared with how it was, taking it in. The garage obviously noticed something amiss because they reported that it had an engine fault, in that the revs were limited to 3,000 whereupon the engine cut out until the revs had dropped down a bit. They speculated it might be a blocked cat and we let them book it in to investigate the problem for this coming Thu. Meanwhile we put a basic code reader on it and got: The first scan was on "Engine" and the codes were: 16725 16490 16556 16514 The second scan was on "ABS" and the codes were: 01314 18265 I understand from others of Wino's and other posts and informations that the last two ABS codes merely point to going to look for engine management fault codes, is that correct? The best informations seemed to be at: https://mechanicalee.blogspot.com/2013/03/volkswagen-audi-skoda-vag-fau lt- codes-engine.html The last lines being a list of possible causes of the error codes. 16725 - Camshaft position (CMP) sensor A, bank 1 - range/performance problem Insecure sensor/rotor, air gap, wiring, CMP sensor 16490 - Manifold absolute pressure (MAP) sensor/barometric pressure (BARO) sensor - range/performance problem Intake/exhaust leak, wiring, MAP sensor, BARO sensor 16556 - System too rich, bank 1 EVAP canister purge valve, fuel pressure, injector(s), HO2S 16514 - Heated oxygen sensor (HO2S) 1, bank 1 - circuit malfunction Heating inoperative, poor connection, wiring, HO2S 4 fault codes and 3 sensors suddenly being implicated, having never been seen before, and the last time I checked for codes was this Sept before the MOT, only getting DTC: 01 00532 - battery voltage too high or too low, (I think in relation to airbag operation?), and not seen since. So when we stumbled upon more than one report of recent clutch changes as being implicated in throwing the timing out with at least two of those codes, 16725 and 16514, we checked this out: Using a mm graduated rod through the plug hole to determine TDC on No.1 cylinder, we observed the angle of the notches on the end of the crankshaft by removing the plastic end covers, and photographed the misalignment that was indeed present, according to forum information that at TDC the notches should align parrallel to the face of the cylinder head. Is that correct, and does anyone have an authoritative source for that information? I ask as I want to be certain of my facts before perhaps deciding I don't want to trust this garage to carry out the corrective work, if they, as it seems were unaware of having caused the fault, and thought it might be something expensive like the cat being blocked which I can't see implicated anywhere, and they seemed in denial and defensive over the fact of whether a prior engine management light was present, and of the possiblity of an unsecured flywheel turning backwards at some point. They also claimed there were no fault codes, but seemingly contradicted that by saying that they would look for historical fault codes as part of diagnosing the cause of the bad running and 3,000rpm rev limit, which would of course have showed up no less if they had checked the codes, and without checking the codes they cannot possibly know that there weren't any as they claimed! Nor can you have the engine management light on and no codes presumably? There is no date time stamp on these code occurances is there? Do they log mileages with the codes? If it is reasonably believed that the business in question cannot be trusted with the work or to take proper responsibility for their mistakes, I understand that we ought to be entitled to engage another business to do the necessary work and report honestly on what they had found. If that matches what we are saying is wrong, and what caused it, I would put in a claim for the cost of that work to the original garage, and be prepared to take out a county court summons to recover the amount, plus costs if they held out, and defend our claim in the court. Unless of course I am persuaded of not having such a case, hence my post. I want to get them to agree in principle to not making a charge if our analysis proves correct, and the whole story, otherwise given their response so far I don't feel confident of honest dealing, or competent work, and would at such a point of refusal tell them I was taking it to an independent garage instead and will charge them for the work unless their report was inconsistent with our analysis of course, but there is no way that this car went in running as badly as it came out, and with these fault codes, and observable bad angle of the cam shafts, so it seems reasonable to assume that it still wouldn't have these problems if they hadn't been precipitated by the garage. We have calculated an angle that we believe the timing to be out by based on the published length of the stroke (86.9mm) and the 11mm we measured the piston rose by before levelling off, after the notches had already aligned parrallel to the cylinder head: 22.78 degrees, which at 10 degrees per tooth (is that accurate?) would indicate at least a jump of two teeth. Have we got that right based on those figures? The actual angle from the photos looked possibly steeper than that, but some of that could be going past TDC, but before the noticeable fall of the piston. Measuring the rise after the point of camshaft notch level seemed a more reliable guide to the actual angle of error though. Finally is it possible for an engine to run driveably, and without damaging anything, albeit under 3,000rpm, which is quite restrictive on this engine, when the timing is out by this amount - about an eighth of the piston's travel to go to catch up with the cam shaft? Best wishes, NeilTM

The whatdunnit is finally solved and fixed, so no more repeat of the intermittent short causing the relay diode to short circuit and the fuse 14 to blow should be possible. My immense thanks to Wino for taking so much time and trouble all the way through this difficult diagnosis and testing, but he really came through, not only with the answers, but posted me a couple of test leads on cannibalised fuse blades for testing the circuit, and to see what was happening while running. Trying to find an intermittent short that has a frequency of every 6 months and 3,900 miles was never a promising prospect, although latterly it not only showed up again immediately after I had conducted lots of running tests, but remained a fairly consistent dead short! That was quite a bewildering (and convenient!) coincidence, and a wonder that I hadn't just blown another diode and fuse. My brother realised that the FET in the ECU was a 'smart FET' that could not pass more than about an amp, and so that route for the diode shorting and fuse blowing as Wino described in note 5 above was ruled out. In fact I think it is probably correct to say that if enough current to short a 10amp fuse had passed through the ECU board it would have left scorch marks and destroyed some components along the way. I'm thinking that the nature of the event in itself weighed against the likelihood that a visually inspected OK board could have delivered such a current, but the Cannock testers said 50/50 chance of it being wiring or ECU. Worth a visual inspection first therefore before committing to expensive testing I would say in these sorts of circumstances. By the time that the very slow first class snail had slime trailed its way to Milton Keynes from Saturday to Wednesday with Wino's test lead for measuring the current draw of the ECU and coils, I think we had already worked out that the culprit had to be leg D in Wino's diagram, the thin .35 blue and green wire that connects pin 86a of the relay with pin 23 of the ECU. Wino supplied me with a link to a video of his test of his wife's Fabia, showing the current draw and pattern of current draw on the multimeter throughout the sequence of ignition on, starting, running, and stopping. I made my own similar video, and it seemed that the measurements were comparable, and so we concluded that the ECU was functioning as it should, and not drawing excessive current as the ECU testers had posited could be a sign of eventual stress failure. Wino and my brother having deduced from an analysis of the circuit diagram that only an intermittent short to earth somewhere on leg D could have shorted the diode and blown the fuse, I set about trying to find out where the short was likely to be. By testing continuity between pin 86a and nearby earth, I was obtaining more or less a dead short. By testing between pin 23 and nearby earth at the other end of the wire I was getting a resistance of .1 to .2 of an amp, suggesting the short was at the relay end and measuring the resistance of the length of the wire. This was then confirmed by measuring continuity from one end while waggling the wires at the other. Nothing from the ECU end of things, but tugging on the wire to the back of the relay socket it became open circuit several times, and shorted, and all points in between, and activity furthest from the relay socket seemed to produce it. We had found which bit of the wire the short was occurring on, but impossible access behind the relay holder, visually and physically, as well as fruitlessly searching high and low for my endoscope, has robbed us of the possibility we may have got a visual of the actual short, and perhaps some idea as to what could have caused a short in a pristine and never visited deep region of behind the dash against the bulkhead. I was able to access the back of the relay plug by cutting through enough of the holder in the empty row above, and filing down some empty bay catches to withdraw the holder forwards and gain access to the wire at the back, leaving as long a tail as we could, thanks to my wife's small hands, to solder a new wire to decently, having first passed one through sellotaped to the end of a rod passed through a 5.5mm hole I drilled through the bulkhead next to the panel through which the cableform wires passed through the bulkhead to six connectors on the cabin side. The length of the wire replaced must be less than a foot, and from two accessible places outside of wrapped cableform, and the new wire takes a straight route through the bulkhead to the back of the fuse holder - all quite ideal really. I grommeted the hole and added sealant where the wire goes through it. Testing for shorting after cutting the wire also confirmed which side the short was, and subsequent testing revealed no shorting at all. Had to take the bonnet off and undo the panel behind which the wiper motor is located in order to remove that to gain access to the panel through which all the wires pass. All straightforward once I had used my large puller to remove the wiper arms which refused to budge any other way. Thanks to all who contributed to making this difficult repair possible, and to be able to be confident that it will not recur.