Breezy_Pete

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

Spoke too soon actually Lee. Bloody thing went into limp mode a couple of miles from destination. Cylinder 2 misfire code plus the precat lambda code. On the end of a whatsapp video chat she's just swapped out cyl 2 coilpack and is heading out for a short range test drive...

Radiator seal might fix the matrix leak, for now, so maybe worth a try. Does the oily film look pinkish if you wipe it away with a white tissue? I can't think what else it would be other than coolant, but a colour match would be good evidence.

I think if your car had an EGR valve, fuse 7 would be relevant to that. Gotta walk the dog, do some work etc. but I'll come back to this later. Are you sure the front oxygen sensor only has 4 wires, I'd expect 5? Are you in Germany or Oxford at the moment?

It seems like the answer to the thread title is no. What I should have asked was - is it time for a new pre-cat oxygen sensor? Replacing that seems to have restored correct function, according to a chirpy voice message I just got from its owner, on the road. Fitted and immediately took some logs yesterday, static and on a test drive. Will review the data later, but it felt better if not perfect straight away. Thanks for the suggestions and comments.

I still can't quite work out the function of that airbox hose. Is there a one-way valve in the airbox; to which it connects? Or a rather narrow orifice/jet?

So where isn't the grommet? At airbox end?

Might just be a VCDS quirk?

Could you take and post a photo of this? I'm not familiar with the breather arrangement on the automatic cars, so I'm not clear what exactly you mean, or what it does. That rings some alarm bells. Has the coolant temperature sensor ever been changed to your knowledge? Later versions of the BKY engine had the EGR valve deleted from the design for some reason. My recently acquired Polo has the same lack. Can't say I'm upset by the absence of something that seemed to cause a lot of problems on this engine family. That spark plug does look odd, but I can't remember anything except additives causing weird colourations? Which oil does it get?

Massive QA fail. Push for some sort of compensation (free brake fluid replacement and oil change?) as well as free replacement with correct part.

Power goes up in proportion to V-squared for a fixed resistance, so it's better than linear. It's not a fixed resistance (nothing much is over the sort of temperature range a bulb filament experiences). Interesting graph relating all the parameters - including lumens and lifetime - here http://www.lamptech.co.uk/Documents/IN Voltage.htm

Yes, unless someone fitted a turbo when I wasn't looking. Got a NOS genuine pre-cat oxygen sensor arriving (hopefully) tomorrow, bargain at <£35 delivered from the bay of e. Took some logs this morning and I think there may be something amiss there. The (only) fault code points to a problem with it; so it seems nutty to ignore that. Can't see anything obviously bust wiring-wise. Can't see anything wrong with the chain timing, although it's a bit tricky to be precise about TDC when you don't fit the crank locking tool, 'cos you've convinced yourself that it's pretty close and so probably isn't the issue. As you say @TMB, if the chain had jumped a sprocket tooth, or was overly elongated, it ought to run poorly all the time, not just in one small area of the operating range.

Tape measure?

I think that demonstrates that you need a new fan control module. (Or there's some wiring problem somewhere near it).

^ Best start your own thread rather than tag onto this one. Clearly a different problem; suggest you research N280.

Evaporator is item 15 here: https://skoda.7zap.com/en/cz/octavia/oct/2016-753/8/820-820020/ Item 11, the expansion valve may be visible at the back of the engine bay, where the refrigerant hoses attach? There really isn't anything else connected to the refrigerant system inside the cabin other than the evaporator itself, and possibly that valve if you can't see it on the engine bay side of the firewall. Their 10% etc. is an initial 'hope he takes this, that would be awesome' gambit, worth pushing back firmly against with considerable justification; that this is a part that should last the lifetime of the car. If goodwill can't do better than that, in these circumstances, I'd be quite surprised. It's not like there's anything you can do as a customer that could damage that part; it almost has to be a manufacturing defect.

Just realised that with two spares available, I could test the remaining two coilpacks by substitution in about 5 minutes flat, in one hit, so I did. It's not them.

Might have to check for chain stretch too; just in case that could be the elephant in the room. TDC no.1 and see what the cam end slots are up to.

Just redid compression test, and all about 15 bar. Had a moment of hope when one of the three coilpacks had some little bumps in the top surface, the other two being smooth and flat. No change when swapping in either of a couple of spares. 😞 Might do similar swapsies with cyl 2 and cyl 3 coils later. Belt and braces. Next stop after that: lambda sensor investigation I think. The 16514 (B1S1 malfunction in circuit) - intermittent had returned, although not enough to put the fault light on. If that throws up nothing, try to find another garage that will really do a leakdown test...

TB is clean, but thanks. I booked it in to a local garage for a leakdown test on Wednesday, then phoned back just now to ask what that was going to cost, cos I forgot during the first call. Spoke to someone different who helpfully admitted that they don't actually have leakdown test kit! 😣 Cancelled that one...

☹️ Oh dear, I did wonder what ever happened with this.

Odd how cylinders 1 & 2 exhaust valves are really badly cracked all around, but cylinder 3's is completely fine as far as I can see in that photo. Anyhow, no wonderfully positive progress to report from a bit of work on ours. Took the spark plugs and coils out for a look, nothing to see. No codes for misfires, so nothing to go on in terms of swapping anything out, even though I do have spares. Swapped in the refurbed injectors; no obvious change to anything. ☹️ Should've done another compression test while the plugs were out, but didn't think of it in my haste to check whether the injector swap had fixed things. The symptoms are much worse during first minute from cold start, if that helps anyone form an opinion. Still very jerky to pull away at operating temp, without adding revs that never used to be necessary. Couldn't see anything useful with USB camera So many things to try, too much glumness ot do anything at the moment

Just to be clear mac, I was laughing at your amusing description of the incident, not mocking your lack of knowledge.

@bTCole Were you undoing the clamp in order to replace this battery? Hopefully, because that yellow foamy stuff is sulphuric acid, and it should be contained within the battery. It's highly corrosive and dangerous to touch. There's actually a rubber drainage pipe connected to the bottom of the battery tray that is supposed to help any such fluid escape, away from metalwork onto the ground. It may be that your entry-point to this pipe is clogged up and so the 'fail-safe' drain wasn't able to do its job. Here's a photo of the far end of that pipe on a Polo, hanging in front of the screenwash reservoir:

Pleasure. 👍