And that drive went OK, but I really doubt it was the coilpack.  Back to believing it might be exhaust valve(s) after all.  🙄

I wonder...I've always assumed that the misfires that go with exhaust valve trouble are due to gas leakage during the combustion event, (why) would that cause misfiring?.

 

But another possibility that's only just occurred to me is that the valve(s) is/aren't actually leaking much at all, but is staying so hot due to damage or just poor seating and consequent poor heat-conduction path into cylinder head; so it triggers pre-ignition??

 

Is that what really happens? Seems a bit 'out there' to me, but I have very little knowledge of the details of combustion cycles, and what goes wrong with them.  

I also have very limited knowledge at this point, but a hot-spot in the combustion chamber can cause ore-ignition and therefore a misfire. 

Lean burn engines rely on surviving very high combustion chamber temperatures, the exhaust valves get much hotter than the inlets and depend on good seating to conduct the heat away from the valve and into the head casting.

The 12V engine is much less susceptible to valve burning than the 6V because there is more surface area to conduct the heat away. 

Correct me if I am wrong but Wino you stated that the symptoms are worse on cold start suggesting it may not be an issue of valves overheating.

Yeah, you're right on that.  

Trouble is, I'm really unconvinced that swapping in another coilpack is going to have helped, cos I've already swapped in different (spare) coilpacks into cylinders two and three, a few days ago, and left them in there. So that can't have been the issue before then, and now. 

Can't help thinking she'll have recurrence(s) of limp mode on the way back on Sunday, due to real fault (whatever the hell that is).

I want to drive out to where she is* in my Polo, swap cars with her and come back in hers. She won't hear of it though cos she has breakdown cover, I don't.

Plus it's no less likely to break down with me at the wheel, really. Just don't want her having the stress and anxiety.

 

Already taught her that cycling the ignition may kick it out of limp mode/cylinder shutdown, at least temporarily.

 

 

Aaaaaaaarghhh!

 

*2.5 hrs away

I've never heard off another rebuilding one and it lasting. Personally I'd be looking at swapping a lower miles engine into it if you like the rest of the car.

3 minutes ago, StevesTruck said:

I've never heard off another rebuilding one and it lasting. Personally I'd be looking at swapping a lower miles engine into it if you like the rest of the car.

 

Interesting thought, thanks.  Would be easier, for sure.

I once had a Skoda Estelle that ran fine until the engine was put under load like climbing a hill, then it would start 'coughing' which felt so much like an ignition problem but turned out to be a small piece broken off an exhaust valve. Would have put money on it being an ignition issue - especially as it ran fine until put under load.

I think it's high time I worked out how to get an upwards view inside these cylinders, especially no. 2. 

I know I could get the head off in very little time, but it'll take me ages to get it all back together, and I'll be so upset if - when I get in there - there isn't any sign of trouble that would justify the removal!  

If it wasn't for the silicone sealant everywhere, cam cover to head, timing cover to everything, sump to block and timing cover, it would be much less onerous.

I just watched a youtube video that set me back on the right track.

Bloke inspecting valves with an endoscopic camera. 

 

My mistake was trying to use this tool to look upwards. The right way to do it, is to use it (with dinky little mirror at 45 degrees) to look sideways...

 

If the car will just make it back here...

I've thought of a compromise on the 'if the car will make it back' issue.

If I set out at roughly the same time in my Polo, with VCDS laptop on board, and tools/spares in abundance, we should meet somewhere in the middle after a bit over an hour (provided we agree on exact route!) and can continue in convoy for the remainder of journey.  Think she might go for that, and I'd be a lot happier that way.

 

Gonna practise my endoscopy on my Polo later on today.

Car made it back without so much as a warning light. 

 

Endoscopy tomorrow evening, I hope. 

been reading this and at some point it looked like you have fixed it but sadly no 😞 

some very intelligent people on here  

i really do hope you fix it wino, good luck my friend 🤞👍

My 45-degree mirror showed up, and I was able to get a pretty fair view of all 6 exhaust valves, though I'll be having another go when I've more time and maybe an extra light source.  Nothing suspicious seen.

 

Understandably the owner doesn't trust it just now, so we'll swap cars for a bit, and I will see how it fares. 

 

Presently working on the sketchy idea that maybe the new oxygen sensor did fix the problem, but messing about swapping in coilpacks just before that actually introduced one that was starting to fail. Might try to autopsy that coilpack later, but not sure I'll have much time today.

Some progress today, at long last.  

Plan for the day (off) was to start off by substituting back in, in a different cylinder, the coilpack that got changed out last Friday.  Idea being, see if it really is faulty, and if so the fault should show in its new home cylinder.

Then I had in mind to unplug engine ECU connections, and pre-cat oxygen sensor, inspect all for corrosion etc. and check continuity and for shorts on the wiring from ECU to the sensor.

After that, I was planning to go a bit deeper into the chain timing by fitting the crank locking pin and then seeing how far out, if at all, the cams were from their proper angles.

 

I did the coil swap/shift, and that suggests there was never anything wrong with the coilpack.  No misfires, no fault codes, at any engine temperature.

I did inspect the engine ECU connectors, which were spotless, but didn't do the continuity testing 'cos something else occurred to me while I was looking into the bay.

 

@sepulchrave mentioned air leaks early on, and I didn't do anything with that suggestion except have it in the back of my mind as something I should check.

I found myself staring at the PCV valve and a dead easy experiment occurred to me.  With engine running, I put my finger over the pressure-equalising port, expecting to maybe feel a bit of oscillating air but not to have any effect on the engine.  That didn't happen.  As soon as I put my finger over it, it stared squealing loudly, with frequency diminishing with time, and the engine bogged down and cuts out completely if I keep my finger there.  Veeeerrrrry interesting.  That port shouldn't be sucking, it's supposed to just let the diaphragm move in response to inlet vacuum levels, which would be harder for it if the space above it was a sealed cavity.

 

So I borrowed the diaphragm/spring/lid off one of my Polos (different breather arrangement, but same type of PCV valve). Bit of a battle to unclip it down the back of the Polo engine, but plug and play onto the Fabia.  Now if I put my finger over the pressure-equalising port, it makes no difference to the engine running. And it makes no noise.

 

That could be the end of this! Thanks sep. 

Lots of test driving to do to re-establish confidence, but I have a good feeling about it.    During a shortish test drive just now, I even think the brake servo function might be better than it has been for some time, possibly because inlet vacuum isn't being spoiled by breather malfunction when the throttle is fully closed? The owner has just taken it on an urban drive; I'd be over the moon if she notices the brakes are working better (and if the car runs OK! )

 

 

Interesting stuff. Fingers crossed 🤞

Went for another, faster test drive and all was well. The braking improvement is stark. I must search out the thread I started about this car's brake deterioration, to see how long ago it was. Gut feeling is it may have been two or more years of 'half assed servo'.

14 hours ago, Wino said:

Gut feeling is it may have been two or more years of 'half assed servo'.

Four years!

 

You have hopefully got it sorted, sometimes its not easy to work out what may be the issue at least you didn't remove the head.

 

Well overdue for an update on this.  I think it  is going to be time for a refurb, but not the one I expected. 

The leaky PCV system fix has made it run without fault codes or warning lights, but the extreme judderiness of moving off unless revs are first spiked remains.  I experimented with blaming the clutch hydraulics but got nowhere fast other than to confirm that for some reason all the clutch disengagement/engagement happens at the very bottom of the pedal travel, for reasons unclear. I (now) don't think that is actually anything to do with the strange behaviour of the engine.  Will be playing about with extending the slave cylinder actuator length in due course as a possible fix that doesn't involve gearbox off.

 

Endoscopic inspection of the exhaust valves suggests nothing obviously amiss there, but the elephant in the room - I think - might be the timing chain.  At 175k miles with no record of it being anything other than what it left the factory with 15 years ago; surely it's getting tired?

 

If you've seen one of these chains, and the sprockets it runs on, in the flesh, you'll know that this is barely more robust-looking than something you'd find on a pushbike.  the tensioner is also pretty primitive, with no ratchet mechanism to stop it being pushed back if the forces on it aren't balanced by oil pressure.  I've had the full kit of chain/sprockets/tensioner/seals/bolts kicking about for some time, so there's little to buy.

 

I've recently stolen from ebay (£12.50!) a much more recent oil pump of the right part number, which incorporates the pick-up strainer and is immaculate, so that will go on too, and a coolant pump that I similarly acquired a while back may be included in the refurb too, although that isn't camchain driven so needn't be done simultaneously.

 

Got myself mighty confused earlier trying to research the (biiig) crankshaft pulley counterhold tool, which I'd seen used on youtube just this morning by some German fella working on an AWY engine, but couldn't find any reference to it in the erWin literature for this engine (AZQ).  Everything official seemed to suggest that the crank locking tool that inserts where the crank sensor goes was all that is required. Now I've never fitted that tool, but I home-made one about 8 years ago, not long after acquiring the car. It's just mild steel so I'm not sure I trust it against the 150Nm + 180 degrees tightening regime for the crank bolt. I suppose it has a good amount of leverage at the periphery of the flywheel, but I might play it safe and invest £25 in this: https://www.ebay.co.uk/p/1845066239

 

The reason for my confusion turned out to be that it is specified for the same bolt on the 1.4/16v engines, and had been discussed recently on here.  So I'd have it for whenever I get round to either of the overdue cambelts on my Polos...

 

@Tech1e, I should just buy that, right?

 

 

 

 

Edited 29 July, 20205 yr by Wino

Made a start yesterday, and I'm glad I bought that counterhold tool.

 

Early setback hit me when having got the inlet manifold off, and the crank sensor out (with a fair bit of wiggling and wriggling), the locking tool wouldn't go into the big hole in the block.  

The aluminium of the casting has suffered that furring/oxidising over the years and narrowed that hole down a fair bit.  Access to clean it up is challenging, even with inlet mani off.

Decided to lock the cams and then feel for the slot in the flywheel with the biggest Allen key I could fit in there. Turns out the slot is about 5mm ahead of correct alignment, as far as I could judge with that crude method. That seems consistent with some, but not much chain elongation.  I carried on and got to this point yesterday:

 

The sump is loose but just hanging off a couple of screws. Tensioner part number ends in an N, and cam sprockets are date-coded late 2004, so it's fair to assume this is the factory original timing kit.

 

Big decision now is whether to swap out head and cam stuff while I'm this deep into it.  Have a feeling I'd regret not doing, as the first step of the head job is to get to this point...

On 26/06/2020 at 21:44, StevesTruck said:

I've never heard off another rebuilding one and it lasting. Personally I'd be looking at swapping a lower miles engine into it if you like the rest of the car.

Turns out I really should've gone down this path. 

 

Despite solving the judder/clutch problem, and refurbing the top end and chain stuff, she's still 'orrible sounding and looking at idle, and I'm thinking that at 177k miles this engine block is 'over'.

Replacement should be turning up on a pallet this morning, and have today/tomorrow set aside for the swap.  What checks ought I to do on it while it's on the pallet? Thinking I probably oughta check the chain timing with the locking tools. Probably plugs out for a check too. Anything else? @Tech1e, your advice would be very welcome, as would anyone/everyone else's.

 

Cheers.

Hi Wino,  I would be asking the same questions  but what about dropping the sump to look for metallic residue in the oil and oil pick up strainer, not so easy on the pallet though, having said  I hope you have got a good one and all goes well.

Martin

What to check on the replacement engine turned out to be a premature concern, as it didn't turn up at all this morning, or any other time before close of play. 

 

Good progress on removing the old. Front of car pivoted out the way, engine crane supporting the engine, now connected by nothing but a couple of bolts.

 

Small independent courier operating as a local depot for Palletways have it booked for delivery tomorrow by 11am. Frustratingly it's only about 3 miles away.  If it doesn't make it by 11 I'm going to go and get it with my trailer.  They claim most of their drivers are off sick with Covid. Could be true.