Festival of warning lights and beeping!

Yes it could be the source of your air leak reported fault I think.

I was part of a recent FSI discussion that included this charcoal filter but a large part must be the same for your 1.4 both being petrol. In a nutshell from what I remember the charcoal filter sits on a vent line from the petrol tank, a solenoid valve (you spotted) opens and and allows unwanted vapour to discharge into the inlet manifold. So a leak in the line will appear as a leak from the inlet manifold. For some weird reason I think I also remember the charcoal filter on your 1.4 is located behind the front O/S wheel arch liner???


Hope this is of some help.

Andy
 
You are onto something, snap, you are not alone, a blast from the past but lamentably no posted solution.


Andy
 
Thanks so much for those links Andy - that all sounds very familiar.

I'm still not really sure what I'm looking for, but I think an exploratory look behind the arch liner is in order, once it stops raining.

I also note that on the thread about the FSI there was some talk about a poorly sealing fuel cap being an issue, so I might look into that too.

I wonder if anyone can confirm: is it the case that this system is just to allow fumes from the tank to vent into the inlet manifold while the engine is off? That is, so that they don't pressurise the tank too much in hot weather? And if that were true, then presumably the solenoid valve is supposed to be closed when the engine is running, right?

I'm just wondering if the noise I heard, the same noise as Angelo reports on that other thread, is actually resonance from the engine - maybe the valve is open when it shouldn't be, and the engine is sucking through the canister, causing the effect of an air leak, and also generating a noise as the engine pulls through the canister. Just a thought!

Would be extremely grateful if anyone can confirm or deny the above! :)
 
I would say clamp it, vac line is used to actuate it, by default It should be closed, pinching the line would only stop it from opening.

Does not sound like something dangerous, but also damn if that is the issue, that is some gremlins.
 
Try it as temp fix. If the Xmas tree of warning lights stops then you have likely found your air leak


Sent from my iPhone using Tapatalk
 
So, a quick update...

I made a clamp for the tube, and I replaced the knock sensor.

Clamping the tube might have done the trick re the festival of warning lights. The same sort of shunting about that caused issues before now do not trigger any dashboard explosions. Fingers crossed that has done the trick. I would be interested to hear if anyone knows of any long-term badness that could result from having this hose clamped.

Replacing the knock sensor has not helped. After a few minutes idling the engine starts to misfire on cylinder 2. To be fair the new knock sensor wasn't quite right, as the connector wouldn't plug all the way in until it clicked. Not sure why that would be, but as long as it's making contact I can't see why it wouldn't work properly. Pretty annoying, as I also can't imagine the car passing an MOT with a misfire.

I don't know if it's poor form, but I might start a new thread just about the misfire - someone else must have surely worked out what the issue it with AUA engines and misfires on cylinder 2 by now!
 
So, a quick update...

I made a clamp for the tube, and I replaced the knock sensor.

Clamping the tube might have done the trick re the festival of warning lights. The same sort of shunting about that caused issues before now do not trigger any dashboard explosions. Fingers crossed that has done the trick. I would be interested to hear if anyone knows of any long-term badness that could result from having this hose clamped.

Replacing the knock sensor has not helped. After a few minutes idling the engine starts to misfire on cylinder 2. To be fair the new knock sensor wasn't quite right, as the connector wouldn't plug all the way in until it clicked. Not sure why that would be, but as long as it's making contact I can't see why it wouldn't work properly. Pretty annoying, as I also can't imagine the car passing an MOT with a misfire.

I don't know if it's poor form, but I might start a new thread just about the misfire - someone else must have surely worked out what the issue it with AUA engines and misfires on cylinder 2 by now!
The fuel tank EVAP system collects petrol vapors and under the control of the valve shown in your photo above adds them to the engine intake to burn. The fuel system is normally sealed so the vapors don't escape and cause pollution. If you have as leak somewhere, when the ECU opens the EVAP valve you get too much air going in and this makes the engine run lean. The same thing would happen if the valve is faulty and open all the time (it should be closed when not energised). A leak could be anywhere from the pipework back to the fuel tank, the vapor collection canister or even a badly fitting fuel filler cap.
Note that the ECU expects additional fuel to be added when the valve is open so if it has no effect then this could cause problems. As the EVAP system is part of the emissions control then a detected fault may illuminate the check engine light. If you do have a leak in the EVAP system then blocking the hose at the engine will just let the fuel vapor escape into the atmosphere (just like very old cars!). If there is no leak and the valve is faulty then blocking the hose would allow the fuel vapor to build up until the excess pressure release vents the system!
 
Well I certainly have managed to make things worse! ?

That first test with the hose clamped was obviously just a fluke, as the same problem came back with a vengeance.

Then I found yet another thread by someone with these exact same symptoms, and they suggested that it could be the EGR valve playing up. Armed with this new information, I got up early and used the gasket at the throttle body end of the EGR pipe to make up a little aluminium blanking plate, which I then sandwiched between the pipe and the throttle body with a little silicon instant gasket for good measure.

I left it to cure for a few hours and then tried the car. Worse. Much, much worse. The triple warning lights came back on almost right away, and once the car was warm I got a whole new exciting set of problems!

NOW when starting the engine it will either...
  1. Not tickover properly, hunting around and eventually dying completely, or
  2. Tickover at 1200rpm, but the throttle no longer works at all
To illustrate, I recorded some vids of the dash:

Won't tickover - https://photos.google.com/share/AF1...?key=cFV1aTROdGFabXFfYWNkYTMxM0xaZlZWQ1FqUzln

Throttle pedal disabled - https://photos.google.com/share/AF1...?key=YldmdFI3X1UtWlBCcThLNm8ybVYxNGhxU3RqLUFB

Incidentally I am still only getting the same three fault codes:
  • 17961 - altitude sensor signal / intake manifold pressure implausible ratio
  • 17912 - Air intake system leak detected
  • 01314 - Engine control module (in the ABS section on my scanner)
 
I would guess with EGR letting air in error was less for what ECU saw for air flow, blocking It off ECU potentially sees more wrong as instead of reading some air and assuming it is through EGR it sees no air from EGR thus more air from unknown.

It is doing exact thing as what mine did, if you remove blanking plate from EGR and leave it about 1/5 open it should do this exact thing, and when you put the pedal down it will likely start moving up and down in revs (or the other way around, cannot recall the behaviour exactly).

it is probably hard to tell, but I would imagine there should be an air whooshing noise, like from a draft though hard to tell with motor running. It threw me off on mine as I suspected throttle body, due to whoosh being next to it and seeming like it was the valve stuck closed.

I've tried moving throttle valve by hand a bit and it would somewhat rev it up and down as normal too, but it would not react to throttle pedal due to the leak and ECU not being able to make sense.

Sounds like a bit of a faff, but could you record a video going over the engine bay from side to side few times with engine running? Frustrating as this feels very familiar.

Also try unplugging air flow(pressure?) sensor (it is in the manifold, on the left hand side lower down as you stand looking at it with bonnet off) and see if that changes anything if not tried it yet?
 
Sounds like a bit of a faff, but could you record a video going over the engine bay from side to side few times with engine running? Frustrating as this feels very familiar.

Also try unplugging air flow(pressure?) sensor (it is in the manifold, on the left hand side lower down as you stand looking at it with bonnet off) and see if that changes anything if not tried it yet?

Happy to oblige if there's even the slimmest chance of a solution! :)

Moving side to side over the engine bay - https://photos.google.com/share/AF1...?key=R0dWaEFSZTlPRFhpaEt2U0FSeHlKaHRkdEVsSHd3

The MAP sensor is new, but I tried switching off the car and restarting with that disconnected, but alas it made no difference.

A couple of things occurred to me while I was doing all this:
  1. The first fault code talks about the ratio of the altitude sensor signal to intake manifold pressure. Is there really an altitude sensor? And if so, where is it?
  2. It seems odd to me to get a fault code in the ABS section on my code reader. I guess the brake servo is still powered by vacuum from the engine, right? Could that be related somehow?
 
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from what i understand the ABS fault is triggered due to the engine somehow, not really dug deep enough to find out why it makes sense to the ECU, as once I sorted the leak it was happy and all the codes went away.

Far as I can tell the MAP sensor plays the role of altitude sensor as well, or it calculates from MAF and other sensors.

Will give it a listen with decent headphones at home, but to me it does sounds like a hiss on the right, could just be the phone mic too I suppose.

Could try to remove that intake pipe from throttle body and see if valve moves, mine was solid closed throughout without any movement throttle pedal or not, cover it and see how much air moves past with it closed, it should stall pretty quick with air supply cut off if you cover it with a book or something else flat and solid, if it does not it might highlight the whoosh of the leak.

or if you're a smoker/vape/incense could puff some smoke in there and see where it goes, as it should be fairly stale around manifold and throttle body especially when engine is cold and fan is not on, the suction/vacuum in the intake should be pretty strong, in my case even when it looks for idle like that the butterfly valve in intake was not moving at all from shut.

edit: cant hear anything obvious but it sounds smooth to me minus the bouncing. did you check the hose behind intake as need to give it a feel.
 
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Last post for today (mainly because if I stare at this broken engine any longer I may lose the will to live) - here is a quick vid of the engine running without any of the airbox addenda attached - https://photos.google.com/share/AF1...?key=eE4yMk1DOHlOdDJkbFpXRVhjdXNHZXlsLVVSX1Fn

As you can see, when I put my rubber-gloved hand over the throttle body it stalls right away, and the suction on my hand doesn't dissipate.

Prior to recording this I tried just standing there for ages to see if the suction would go. It did diminish a little after several minutes, but I would have thought the sort of leak that would cause this kind of poor running would be big enough that the vacuum disappeared pretty quickly.

In fact, what really baffles me is that running this way, with the throttle body open to the air, I can't imagine any leak would really make much difference, or even be detectable, but the same fault codes and poor running remain.

Apologies if this is a stupid question, but is there any way the timing could be out? As I've said before, carbs and a dizzy are probably more in my comfort zone, and if this engine were an old one I would immediately think the timing was out. It sounds diesel-like at very low revs, won't tick over, but then clears up as you rev it. Can a car with a coil pack have wonky ignition timing, or is that just not possible? Apologies for my ignorance!

One other question - when I replaced the MAP sensor and cleaned the throttle body, was there any sort of procedure I should have undertaken to get them to talk to the car correctly?
 
Any idea what subsystem the fault code might appear under?
I recently did a scan for @Mark F and we got the same fault code - it is under module 03 (Brakes)

VCDS-Lite Version: Release 1.2
Sunday, 27 June 2021, 11:05:51.
Control Module Part Number: 8Z0 907 379 B
Component and/or Version: ESP 20 CAN V015
Software Coding: 10758
Work Shop Code: WSC 02154
VCID: 47E1D81F76B5
3 Faults Found:
01314 - Engine Control Module
79-10 - Please Check Fault Codes - Intermittent

Have a listen at his engine noise too, is it similar to yours? https://www.a2oc.net/community/index.php?threads/need-help-or-advise-please.47021/post-450864

Edit: Your question had been answered of course, I just hadn't read the whole thread yet! I'll leave it though for the second bit.
 
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it could be cam timing, reading other articles on it. Guess It has been barking up the wrong tree, though fault manifests exactly same as the leak I had.

ignition is controller by ECU so it does not have timing like older systems.

It might be worth having a look at MAP/MAF real time reading to see what the ECU sees, in case values are way out?

After replacing and patching the hole I did need to clear codes and took a few start stops until it started running alright, could be worth unplugging battery for a couple minutes to see if that makes it run for a bit.

If it is not leaking in air I would guess a vacuum line or a sensor fault, apparently leak in hydraulic system can bring up similar error, though not seen any examples.

This was a read that helped me with the leak, if not linked yet, though again it feels more like a vacuum line or a sensor at this point that makes ECU think it has a leak, will likely be a challenge to track down.



Could be worth checking for articles of polos having these errors as well, as 1.4 in polos is very similar.
 
@Cenick very kindly popped over and did a scan for me last night with VCDS.

Thanks to that scan, I now know that my own scanner isn't showing me the whole picture. There was (as someone suggested earlier) an intermittent fault with the yaw sensor, which I couldn't detect using my gadget.

However, unless someone wants to tell me different, I can't see any way that that could cause the car not to idle, and to sound like a bag of nails!

Was also good to have another A2 owner hear the engine running and confirm that it sounded as bad as I think it does. I've never heard another A2 1.4 running, so have nothing to compare it to. But Steve agreed it really does sound rattly (diesel-like even) and loud. It does indeed sound very much like the example posted above by @herx !

I think I'm now satisfied that there is no leak. I reckon if covering the throttle body kills the engine, and the vacuum doesn't die away very quickly, then there simply cannot be an air leak.

All of which only seems (to me) to leave very few options:
  1. Some sort of sensor failure or calibration issue that doesn't generate fault codes, but does mess with the fuelling or spark timing in some way
  2. The cams are timed incorrectly. The engine was apparently replaced about 18 months before I bought the car. The receipt was sound, but I've no idea of the provenance of the engine. The receipt does say that the cambelt, tensioner and waterpump were done at the time. Could one cam be a tooth out? Guess I'll need to find out how they should be lined up in order to check!
  3. Something else mechanical, like a knackered valve train, blocked exhaust etc etc. Feel this is less likely simply because on the occasions when I can get the engine to run, it revs perfectly well.
Thanks to everyone so far who has offered advice - I just hope that this is something I can fix for less than it cost to buy the car!
 
Take a look at these articles Martin as these may help diagnose the poor running.





Sent from the future
 
Take a look at these articles Martin as these may help diagnose the poor running.





Sent from the future

I should’ve read the thread as I see this has been posted previously


Sent from the future
 
The Skoda one is very interesting, though I'm not sure I can see how a poorly fitting oil cap could result in this type of rough running - would have thought an engine should run just fine with the crankcase breathing to the open air. Worth a check though! :)
 
Nuts - there's nothing wrong with the cam timing. Or at least it looks fine to me. Was really hoping that would be the problem...

IMG_20210703_132008~2.jpg
IMG_20210703_131849~2.jpg


Ah well - another possibility checked off, I guess.
 
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