Hi All, expertise of this group really needed...

 

Superb Mk3 2.0 150bhp DSG. Diesel. 160,000 miles, 2015. Fully Skoda main dealer serviced since beginning, always at correct intervals. 

 

For a few months my much-loved Superb combi is cutting out, seemingly randomly. Can happen pulling away, driving slowly or more scarily as in a few days ago, while overtaking at speed. Dash lights up as per attached image. Generally engine management comes on, and occasionally the glow plug light flashes. Car will occasionally restart itself while driving (after a few white knuckle seconds), but always into limp mode. A pull in, switch off and wait 20-30 secs or so and a manual restart normally works fine , with ALL error lights cleared (now and again, it can sometimes struggle i.e. turns over but not catch; waiting for a minute or so will lead to successful restart, similarly all errors will clear). 

 

Perhaps noteworthy it has been eating oil for a similar period, about a litre per 1-2 tanks of fuel (500-1000 miles). There is a strong oil-like smell (though not a burnt smell) around the engine compartment and slightly in the cab. MPG feels low but driving is mixed urban. Most daily trips are 40-50miles return.  OBD reader says no codes. Battery checked with multi meter (hour after stopping) and is 12.7v.

 

Presumably related, the car can 'jump' abruptly when driving. Almost like the brakes were tipped, or hit a bump at speed. (This is normally a single event and doesn't cause a stall). Gear doesn't change or slip. Skoda dealer has replaced 4 injectors (at quite some cost) but the problem persists. They also examined the engine cabinet and reported no evidence of oil loss there.

 

I really am at a loss, and now worried, particularly with no codes reported. Previously it might be once every week or two but its getting more frequent. Any and all insights and advice would be gratefully received.

 

Hello, multiple fault reports such as you have posted seem to be common with battery issues - have you tested battery while cranking the engine?

Another possibility reported on some other postings is crankshaft position sensor fault.

@Warrior193 Thanks for feedback. Haven't tested battery while cranking yet; what should I be looking for?

 

Re: crankshaft position sensor fault, I have seen this mentioned alright. Should I expect to see a fault code here if this was at fault?

 

 

I'll check, but IIRC voltage at terminals should not drop lower than around 11 volts on engine crank - ideally, prevent engine from starting during test if possible.

Do you know if the battery is original?

I have the exact same issue. I hope it is a battery and not a mechatronics unit

Fitted new battery, no difference

17 hours ago, geezer1000 said:

I have the exact same issue. I hope it is a battery and not a mechatronics unit

For your sake and mine, I sincerely hope not. I am already down €2,500 for 4 injectors replaced…

@ReaF Do you have VCDS? I'd say your best bet is to take dome live data and try to recreate the issue when driving, it'll capture something. I'd have suggested crankshaft sensor too but they tend to break down under heat and it takes a lot more than a few minutes before starting becomes possible again, up to 1/2 hour in my experience.

 

As to the oil usage, if there are no obvious leaks then you need to do a compression test.

 

Also, as stated by @Warrior193, test the battery on crank rather than resting.

 

Curious to know why the dealer replaced injectors too, was there a fault code on them?

Dealer advised as follows: “Return flows on all injectors are excessive” and recommended replacement on what they termed a “high mileage car”. 

 

Noted Re:  @Warrior193’s advice. Now need to learn the correct way to do this…

 

Dont have VCDS unfortunately 

Crankshaft speed sensor (G28) failure is a common hot engine problem and almost never generates a fault code, being attentive to the rev confer reading during butt clenching failure can be very helpful.

27 minutes ago, Crasher said:

Crankshaft speed sensor (G28) failure is a common hot engine problem and almost never generates a fault code, being attentive to the rev confer reading during butt clenching failure can be very helpful.

If that sensro was the problem would it not just leave the car hard to start rather than stalling and gears clunking?

31 minutes ago, geezer1000 said:

If that sensro was the problem would it not just leave the car hard to start rather than stalling and gears clunking?

Never quite sure if it’s a gear thing tbh. The ‘jump’ is like a touch of the brakes, a sort of lurch. There’s no perceptible rev change. No grinding or strange gear shifts etc. And drives very smoothly between events. 

Or maybe that’s just blind optimism on my part…. 🤞

22 minutes ago, ReaF said:

Never quite sure if it’s a gear thing tbh. The ‘jump’ is like a touch of the brakes, a sort of lurch. There’s no perceptible rev change. No grinding or strange gear shifts etc. And drives very smoothly between events. 

Or maybe that’s just blind optimism on my part…. 🤞

Exact same thing is happening mine at the minute.

1 hour ago, geezer1000 said:

If that sensro was the problem would it not just leave the car hard to start rather than stalling and gears clunking?

 

Once the engine dies it will not restart whilst hot. This happened to me in a Vx Signum. Coughed and spluttered for a sec at 50mph and on I went. Slowed down for rush hour traffic and the car died, right as the two lanes merged into one meaning I had cars going round both sides of me, I identified as a traffic island for a while. Breakdown called and they alerted the police (I obviously needed more people staring at me) who kindly got me to a side road. Breakdown arrived after 45 mins and I explained the symptoms only to be told I must be out of diesel (3/4 tank). Fecker jumped in and the car started first time!

The G28 sensors are known to suffer heat related failure and not to leave a code which makes them harder to diagnose. With the symptoms mentioned and especially the rev counter behaviour, it makes it certain for me without doing direct diagnosis such as logging the G28 signal. Also, the G28 is just about the only sensor that will cut an engine instantly if you disconnect it when running.

5 hours ago, Crasher said:

The G28 sensors are known to suffer heat related failure and not to leave a code which makes them harder to diagnose. With the symptoms mentioned and especially the rev counter behaviour, it makes it certain for me without doing direct diagnosis such as logging the G28 signal. Also, the G28 is just about the only sensor that will cut an engine instantly if you disconnect it when running.

Very interesting @Crasher  First time I’ve seen this suggestion come up. What’s next steps you think??

What is the VIN?

On 25/05/2024 at 12:53, Crasher said:

What is the VIN?

Hi @Crasher  

TMBKH7NP7G7027925

Presented with this I would certainly go for the crank speed sensor 04L 906 433 B first with a good conviction it would solve the problem

 

 

@Crasher and others...thanks a mill for advice. This site really is a fantastic resource. (Though it does raise some awkward questions about the competence of main dealer if I have to come here to try and get help to diagnose a troubled car....)

 

Anyway, thanks again. Once I have job done I'll report back-hopefully positively!- to update info for others. 

Don't get me started on main dealers! I did the first brake fluid change on a very long standing customers new purchase A3 last week, a service was was included in his deal but not the brake fluid change, so I did it and he took it there for the service; they refused to clear the dash service warning as I had done the brake fluid even though we are an independent repairer with VAG and access to the Digital Service System even though I had entered the job as an additional task and printed out the certificate. If Sytner Audi Nottingham ever want to know why we do more Audi's than anything else, I say look in the mirror! Bunch of Cntsu 🙄

For a service that should be based on trust, it’s a shame some don’t subscribe to that view…

 

On the flip side, after a white knuckle motorway ride across the country to south west coast early this morning with not one but three limp mode  occurrences (all resolved by pulling in and just restarting) I went to another dealer, just to see if they’d read codes and let me know was it safe to return drive tomorrow. They were very helpful (as they had been at Christmas 2 years ago staying late to fix a non-closing boot hatch so we could return to Dublin).  

Results  highlighted…..crankshaft speed sensor (!!) and lambda sensor. So…a clear hats of to @Crasher @petrolcan and @Warrior193

 

Thanks for reporting back, was the crank sensor replaced on this latest dealer visit - and how is it running now? 

10 hours ago, ReaF said:

For a service that should be based on trust, it’s a shame some don’t subscribe to that view…

 

On the flip side, after a white knuckle motorway ride across the country to south west coast early this morning with not one but three limp mode  occurrences (all resolved by pulling in and just restarting) I went to another dealer, just to see if they’d read codes and let me know was it safe to return drive tomorrow. They were very helpful (as they had been at Christmas 2 years ago staying late to fix a non-closing boot hatch so we could return to Dublin).  

Results  highlighted…..crankshaft speed sensor (!!) and lambda sensor. So…a clear hats of to @Crasher @petrolcan and @Warrior193

 

Is this an Irish dealer? My local dealer is useless - too big to care

10 hours ago, ReaF said:

For a service that should be based on trust, it’s a shame some don’t subscribe to that view…

 

On the flip side, after a white knuckle motorway ride across the country to south west coast early this morning with not one but three limp mode  occurrences (all resolved by pulling in and just restarting) I went to another dealer, just to see if they’d read codes and let me know was it safe to return drive tomorrow. They were very helpful (as they had been at Christmas 2 years ago staying late to fix a non-closing boot hatch so we could return to Dublin).  

Results  highlighted…..crankshaft speed sensor (!!) and lambda sensor. So…a clear hats of to @Crasher @petrolcan and @Warrior193

 

 

Who was the helpful dealer? - it'd be good to know for future reference