AWY 1.2 3cyl Limp mode(losing battle)

[Nos]

Hi All,

Over 3 months ago 1.2 AWY started giving me troubles as it starter losing power and going into limp mode at 3k RPM
Quick connect to VCDS initially showed lambda that was replaced but no improvement.
Reading this forum found that it could be bad compression or timing chain. Compression checked and all cylinder showing ok. Timing chain was also replaced but still same problem.
Couple weeks ago the engine light came on and VCDS showed speed sensor error. Cleared error but if I revved engine while stationary the error would comeback and it would not rev over 4k RPM. So had to replace the crankshaft sensor. The sensor was seized and broke off while trying to take it out. This meant the gearbox has to come out to to get it replaced. Anyway the sensor was replaced. There are now no errors in VCDS. The car revs fine while stationary upto red line but still goes into limp mode while driving at 3k.
Any suggestions? I have nothing to grab on, the engine runs smoothly while idling or being revved but cannot find why it goes into limp mode while driving. Are there any tests that I could perform?
Thank you

[AnnoyingPentium]

How are your coil-packs? When were the sparkplugs done? Your issue could be coming from there.

[Nos]

Sparks plugs are new. I do no think that the problem is with ignition coils as the engine would not run smoothly and this is not the case. It revs up fine till the red line while stationary.

[nta16]

Can you run or even better record live data with your scan tool?

 

[Breezy_Pete]

How many miles has the engine done?

Was the tensioner changed with the timing chain?

As a matter of routine I'd suggest close inspection of the brake servo vacuum hose particularly either side of the non-return valve. Also any flexible rubber parts of PCV pipework.

[Nos]

17 hours ago, nta16 said:

Can you run or even better record live data with your scan tool?

 

I can try to do live data but need to know what to look for. Any tips?

9 hours ago, Wino said:

How many miles has the engine done?

Was the tensioner changed with the timing chain?

As a matter of routine I'd suggest close inspection of the brake servo vacuum hose particularly either side of the non-return valve. Also any flexible rubber parts of PCV pipework.

engine is just over 100k.

Tensioner, slides, sprockets were all replaced with the chain.

I have looked at pipework and could not find anything, I'll get through it again and also brake servo vacuum hose.

Edited 24 November, 2021 by Nos

[nta16]

20 hours ago, Nos said:

I can try to do live data but need to know what to look for. Any tips?

Well really everything you can, engine, transmission, body control.  If you have a machine that records live data all the better as you can also go for a drive and see what trips the limp mode.

 

But do not put all your faith in these scan tools and raw error codes as you have to interpret the codes and the car may not give error codes even if there are errors because the level of error doesn't meet the report criteria.

 

I don't know what applies to your car but in the past even a brake light sensor fault would have the very stupid computer program going into a right tizzy flapping their arms about and warning you the car will fall apart unless it receives major attention.

 

Computer programs can do clever things but they are not clever and the programs contain many errors and anomalies, VW for some reason (I wonder why) seem to particularly over-complicated programming so the potential for balls-up is greatly increased.

 

Personally with your age of car I would always start with something that is easy, not cost and very little effort - I would disconnect the battery from the car, and immediately turn on the lights and other stuff to make sure there is no electric left in the call at all, immediately turn all back off so as not to forget to do so later, leave the battery disconnected for hours, overnight if possible.

 

Whilst the battery is disconnected I would take the opportunity to give the battery a long slow low recharge, overnight or even more if required.

 

On reconnecting the battery hopefully the computer will be in a state of calm.

 

Before starting the car you could also plug in your scan tool and delete any scan codes and check they have deleted before starting the car.

 

If it works happy days, if it don't it's cost nothing other than a bit of time and patience (yeah, I know such an old fashioned concept) and if you recharged the battery that's always a good idea at this time of year.

 

Never dismiss low-tech solutions, particularly when high-tech doesn't provide solutions.

 

Good luck.

 

[Breezy_Pete]

40 minutes ago, nta16 said:

On reconnecting the battery hopefully the computer will be in a state of calm.

 

If you mean the engine ECU, I don't think this will be any different after a battery disconnect.

All of the 12V feeds to it are either ignition switched, fuel-pump relay switched or ECU relay switched, so it is effectively deprived of all power each time the engine is switched off, until it is next switched on again.

 

[nta16]

4 minutes ago, Wino said:

 

If you mean the engine ECU, I don't think this will be any different after a battery disconnect.

All of the 12V feeds to it are either ignition switched, fuel-pump relay switched or ECU relay switched, so it is effectively deprived of all power each time the engine is switched off, until it is next switched on again.

 

No 5v?

 

[Breezy_Pete]

Only what it generates for its own uses externally and possibly internally. Both from the 12s. More likely 3V3 internally at a guess.

[nta16]

So no residue electrickery in the computer to gain from losing and depleting all electrickery and basically doing a 'turn it off 'n' on agen', or 5v reference for the VW product.  I've misunderstood VW I thought they were ahead of the game ready for the cheating.

 

I'd still do it as the worst that can happen is the battery gets a recharge and gives it also gives a little respite to the emotions and stress on mental health computer programs put on us all, otherwise computer programmers would be an endangered species, or at least have aching testicles. 😄

 

[Breezy_Pete]

Modern memory tends to be non-volatile, so doesn't need permanent power feeds. 

 

4 minutes ago, nta16 said:

I've misunderstood VW I thought they were ahead of the game ready for the cheating.

I've no idea what you mean by that. 

[nta16]

I was think of the 5v reference too. - 

 

 

 

41 minutes ago, Wino said:

I've no idea what you mean by that. 

You must have missed it, on the news a while back.  😄 - https://www.bbc.co.uk/news/business-34324772

  

[Breezy_Pete]

I'm well aware of the emissions scandal but have no idea of the relevance to this topic/car.

 

There is indeed a 5V output from the engine ECU to a couple of sensors which might be described as a 5V reference, but that may be assumed not to be present when all the input voltages are removed by the various relays and ignition switch..

Edited 25 November, 2021 by Wino
5V ref.

[nta16]

Relevance, over-complicated computer programs and systems.

 

 

1 hour ago, Wino said:

but that may be assumed not to be present when all the input voltages are removed by the various relays and ignition switch..

Now, do I really need to spell out what assume means - nope, I'm going to assume you're already well aware.  😄

 

I'm not suggesting to Nos that he spends money hiring a wolf costume and howls at the moon, the battery disconnect is something he could try if he wants, works with older BMWs apparently and they've been accused of the same dirty dealings as our good friends at VW.

 

Who knows it might be some sort of defeat to the computer program failings Nos has that VW hid in there.  🤣

 

Edited 25 November, 2021 by nta16

[Nos]

The battery was disconnected for a full day when gearbox was removed to push out stuck crankshaft sensor. So ECU had enough time to reset. As for monitoring there are loads of data that can be monitored and without knowing, it would be like looking for a needle in a haystack. I have tried to do that while driving but there is nothing that pops out.

[nta16]

Fair enough about the battery.

 

You need two people if the data isn't recorded as there's no way you should be driving and looking at a screen.

 

What you are looking for say in the engine is readings out of balance and reasonable range, fuel, cylinders, sensor readings.  Not sure what you have or get for transmission but they need to be what the engine wants or needs or the mismatch might put you in limp mode.  The body stuff is any thing that links up to engine/transmission that might throw the computers into a wobblily and car into link mode, wheel sensor, stability, brakes (former a brake light sensor!).

 

You could start the car and look at and scroll through all the data in each section but your problem seems to be whilst running so better to look at data before and after problem point.

 

The sensor you have already replaced ned to have been of good quality otherwise they can introduce their own problems, the sensor need to be at least factory standard but better if you as a generalisation often Japanese companies make better parts (and cars) than German or European.

 

Then you have to consider the crap from diesel that might throw a car into limp, usually you get lights and codes from that though (but who knows).

 

You'd hope to see general communication error codes from bad electrical or electronic connections or cables or computer brain-farts (but who knows).

 

So many variables including even intermittent contributor factors - have you got the ECU wet a while back and now it's frying parts of its own brains.

 

The reason it could be so many things is that if it was one simple to find thing you'd hopefully have it well before now.

 

Sorry I can't help more.