Afternoon all. Sharing a recent intermittent issue on my Fabia Mk3 2016 1.2 TSi. 117000 kms, appealing to your experience. Garage is investigating but no fault codes are showing up.

On start-up first thing in the day, the engine splutters or hesitates for a handful of seconds, sometimes accompanied by significant engine rocking (the alarming bit). Symptom swiftly disappears and the engine goes back to normal with or without a prod on the accelerator pedal. No unusual noises like knocking. Later starts in the day are perfectly smooth and normal.

On one iffy start while under cover I noticed a smell of petrol. In old days (…) some of the symptoms would remind me of a flooded carburettor.

Intermittent issue, happened about 5 times in the past few weeks. Seems to be only on warm mornings (approx. 20 degrees C).

It’s not the brief tappety tick or engine grumble note and mild jerkiness while pulling away. No other signs, no warning lights, engine pulls and idles smoothly, fuel consumption fine, oil seemingly ok, battery good, spark plugs a year old.

Thoughts:

• Have seen this thread, was struck by the ‘bounce, etc’ (!) and temperature, but it doesn’t last that long and hasn’t happened before in 6 years of use. The note avoids specifying what conditions. Could a slight over-topup of oil (possible) trigger this?:

https://www.briskoda.net/forums/topic/504258-a-tsb-from-skoda-on-cold-start-behaviour-with-12-tsis-something-that-dealership-employees-should-be-able-to-explain-to-customers/

• Another thought was a worn timing belt tensioner?

Thanks.

It's easy to check the cam belt, just remove the top cover and look inside, at 117,000 kms, maybe time to check and even replace it, as to "is this the problem?" - I'd not think so.

Coking up of the inlet port areas, might be an issue - that can be checked/cleared by walnut shell blasting, or maybe even dry ice.

Injectors slightly clogging up, you could feed this car with a dose of injector cleaner, as someone has reported on one of these VAG forums that these TSI engines can/do suffer from injectors clogging up enough to cause issues.

Temperature sensor - maybe that is handing duff values when "cold" - that could get checked by using a compliant scan tool.

I suppose someone will jump in with "when was it last serviced - and are the spark plugs getting replaced at the correct time/distance?" - that could be relevant.

Oil level, I'm maybe reading too much into this, but, is the engine oil level currently too high, not good.

It is about the same mileage as my wife's 2015 1.2 TSI 90. Things that sprang to my mind were sensors (error codes are not the be-all and end-all as you have found) the computer systems will compensate for some rough running (they would have to with a VW 4-pot) and margins and parameters can be wide for error and warning reporting. I favour sensor(s) but obviously given all the limitations that's an early over the internet guess.

The cold start behaviour was also in my mind hence the thought of sensor(s) and VW computer systems compensations.

3 hours ago, PaddingtonBore said:

No other signs, no warning lights, engine pulls and idles smoothly, fuel consumption fine, oil seemingly ok, battery good, spark plugs a year old.

Yes my thoughts go to past servicing and maintenance history, the VW servicing and maintenance work are a bit scant and often minimum standards for what might be required, if the plugs have been done, has the engine air filter also been changed and air box and hoses cleaned inside? Also current and past use of the vehicle (lots of short journeys clogging the engine insides up. Have the service and maintenance work been done properly previously (and correct plugs fitted).

Possibly live data at one of these cold starts might be needed to see what the sensors might be reporting at the time.

Another thought might be fuel quality or age recently put in or been sitting in the tank a good while but I've no idea of the petrol type or quality or age where you are (we get changes for (cold) winter).

Do the very dumb computers register where you are and ambient conditions, or perhaps the sensors re telling them another story.

As the issue is just at start up (does sound worse than the usual VW roughness and occasional rougher) so I would do a couple of tank refills of something like Shell V-Power and at same time some Italian tune-up runs once the engine oil has fully warmed (90+c on the oil temperature gauge), high speeds are not required just sustained higher revs over reasonable distances and time out of city or stop/start traffic or runs.

Whoops, I missed the sparkplug info had been given, also forgot to comment on the slight smell of petrol when cold started in a garage, that could just be unburned fuel from the cold start - but made worse by wrong temperature information or some other reason causing misfiring at initial cold start.

Thanks nta16 and rum4mo 👍

The car has been serviced annually, with proper bits (checked) and it’s in for another one now at the same time as the checkover. They’ll do a live check tomorrow, but so far they say it’s a blank on the sensors and readings.

Faulty sensors, EPC came to mind, as did fuel quality (French supermarket and sometimes E10) and coking. But the starting issue hasn’t been consistent or regular. It gets an Italian job up an Alp once a month… I’ll give the injector fluid a go.

I may have overfilled oil marginally I think recently, a dipstick check was 2/3 but I didn’t realise the camber (towards the gearbox end) at that spot, so a cautious 200 ml top up might have run slightly over.

My 2014 1.4 is a bit lumpy on start (and always has been in my 4 years of ownership), the fuel map is enrichened and timing auto adjusts for approx. the first 30-45 seconds and then all is good

14 hours ago, PaddingtonBore said:

I may have overfilled oil marginally I think recently, a dipstick check was 2/3 but I didn’t realise the camber (towards the gearbox end) at that spot, so a cautious 200 ml top up might have run slightly over.

I can't see a marginal overfill causing splutter and shake but I'm curious about the 2/3, if you mean 2/3 between 'Min' and 'Max' because the car wasn't parked level so 200 ml was added then that's fair enough.

On your once a month Italian tune-up Alp runs the fill up before the run try Shell V-Power and next fill up, you really want a couple of full tankfuls to get anywhere, I suggest this also for "service" and/or MoT times too.

The VWSkoda "services" and "maintenance schedules" are as I put a minimum and over here at least, to my experience, getting a Dealership to do more than minimum is difficult they don't even stick to the schedules without being reminded or asked for the work, here we have part fitters, few would be allowed to do proper full diagnosis even if they could and wanted to, other than say there are no error codes showing.

Good luck, let us know how you get on.