Ongoing engine/misfire issues

stoofa · 4 Dec 2016 at 16:39

I've posted this over at Briskoda, but as I did get some responses here I'd like to throw my question out to a larger audience:

Car is as a 2011 Skoda Octavia vRS (Petrol). On starting the car from cold there is a definite misfire. The colder it is certainly the worse it is, but as the engine warms up we get to the point of there always being a slight misfire.
The RPM needle isn't jumping around, but you can feel the slight misfire.
This has been going on a while and felt like it had been getting worse. When driving I was feeling hesitation and worse misfire under acceleration.

No fault codes were being logged. The car went in for some diagnostics and the cylinder 2 misfire count was higher than it should be. Moving coilpacks and spark plugs did not change this - the fault didn't follow the coilpack or spark plug.

Over the weekend we went for a long drive to Folkestone, then to Calais and then back to Cambridgeshire. Once again on starting from cold there was a definite misfire. Under "hard" acceleration the car would feel extremely lumpy. If I backed off then it stopped, but applying acceleration and the same again.
At the same time the engine warning light and ECP lights would blink yellow for a while - maybe 10-15 seconds, before switching off.
If I gently accelerate this didn't happen. For the majority of the journey there and back we sat at an indicated 80mph and the car didn't feel like it was missing a beat, only when we accelerated to get past things and only when I did that with urgency rather than gentle pushing the accelerator. When the lumpy/misfire started, backing off stopped it.

On the way back things came to more or a head. We were zipping along at around 60mph as we were coming to the end of a long, curved slip-road. As I looked on to the motorway I wanted to accelerate at pace to get past a slow moving car in plenty of time before a lorry arrived. I pushed the accelerator quite hard and the engine felt extremely lumpy, extreme misfire and both the engine warning light and ECP lights came on, however we also got a message along the lines of "Engine Fault: Workshop" on the display in the middle of the maxidot. This time even when backing off from the accelerator the lump/massive misfire stayed. I pulled on to the hard shoulder, and killed the engine.
I waited for about 5 minutes before switching back on. We were back to where we were before, a slight misfire could be felt, but otherwise the car felt fine. I got up to speed on the hard shoulder, accelerating quite fast, but not with massive urgency and joined the motorway at about 60mph. I then proceed to accelerate back up to the indicated 80mph, and she felt smooth all the way back home - gentle acceleration, no urgency etc.

One night later, start the car up this morning and the same - slight misfire, slow acceleration all is well.
If I sit in the car and rev it, 3000, 4000 to the limiter it sounds absolutely fine. I can even do this by "plunging" my foot to the floor, instantly hitting the limiter. No massive misfire, no warning lights, it sounds fine. So I'm only experiencing these symptoms whilst driving.

Thanks for taking the time to have a read, I know this is now in essay form

I know I'll need to get this looked at, I also know I'll need to get it repaired. I'm just looking for pointers so I know what I'm looking at before this all gets sorted.

Ta

Lashout_UK · 4 Dec 2016 at 17:24

Injector for that cylinder is on its way out - either that or there's a fault with the loom, but I'd start with the injector.

Entai · 4 Dec 2016 at 17:40

Had an extremely similar series of faults and symptoms on a Renault Clio earlier this year

After several trips to the garage swapping out coil packs, leads, various sensors, injectors and even the ECU, they eventually ran out of things to try and swap, so stripped the engine finding a broken valve spring in the process.

Replaced that and its been fine ever since

-Neil- · 4 Dec 2016 at 21:23

Lashout_UK said:
Injector for that cylinder is on its way out - either that or there's a fault with the loom, but I'd start with the injector.

Sounds like this to me, be careful as it's easy to kill a piston on these engines

stoofa · 14 Dec 2016 at 15:39

Just for completion on this one.
The car initially went to a VW/Audi "Specialist". They also deal with the Revo products - you basically got the idea they knew what they were on about.
These are the guys who said it wasn't coilpacks or plugs and that next step would be to investigate injectors.

So anyway, decided to take a punt and take it somewhere else - your common "garage". Gave him the symptoms, didn't mention the previous "diagnostics" completed by the specialist.

Within 45 minutes they had diagnosed the issue to be a coilpack and within an hour and a half they had diagnosed which one and ordered in the parts.
We had a quick discussion about the plugs - they were starting to look a little worn, which was right for the miles since they were last changed, so I had a new set put in as well.
£181 for labour, coilpack and a set of plugs. Car running smooth, accelerates lovely, feels like it did when I first got it.

Suffice to say I've now written to the first garage politely requesting my diagnostic charge refunded as the only thing that came out of that as them telling me the coilpacks were fine.....and they weren't.

Dangerous Dave · 14 Dec 2016 at 18:33

That would annoy me, it basically means they didn't do any proper diagnostics as moving the spark plugs/coil packs would have shown where the issue was.

-Neil- · 15 Dec 2016 at 18:15

Good to hear it's a simple fix

Mrjobby · 16 Dec 2016 at 11:37

Entai said:
Had an extremely similar series of faults and symptoms on a Renault Clio earlier this year

After several trips to the garage swapping out coil packs, leads, various sensors, injectors and even the ECU, they eventually ran out of things to try and swap, so stripped the engine finding a broken valve spring in the process.

Replaced that and its been fine ever since

This boggles my mind.

Nobody thought about a compression test at any point which takes minutes to do.

HummuH1 · 16 Dec 2016 at 12:41

stoofa said:
Just for completion on this one.
The car initially went to a VW/Audi "Specialist". They also deal with the Revo products - you basically got the idea they knew what they were on about.
These are the guys who said it wasn't coilpacks or plugs and that next step would be to investigate injectors.

So anyway, decided to take a punt and take it somewhere else - your common "garage". Gave him the symptoms, didn't mention the previous "diagnostics" completed by the specialist.

Within 45 minutes they had diagnosed the issue to be a coilpack and within an hour and a half they had diagnosed which one and ordered in the parts.
We had a quick discussion about the plugs - they were starting to look a little worn, which was right for the miles since they were last changed, so I had a new set put in as well.
£181 for labour, coilpack and a set of plugs. Car running smooth, accelerates lovely, feels like it did when I first got it.

Suffice to say I've now written to the first garage politely requesting my diagnostic charge refunded as the only thing that came out of that as them telling me the coilpacks were fine.....and they weren't.

You might want to hold on to that letter for a month or so. Not uncommon for coils and plugs to be changed only for the misfire to re-appear on TFSI. Poss more likely to be an injector or carbon-build up on valves. Don't see how they could accurately diagnose Coils and rule out injectors in 45 mins.

Good luck though and really hope it has sorted it, nothing worse than chasing a misfire on a TFSI when it's not an obvious cause. Been there myself.

stoofa · 16 Dec 2016 at 22:05

Mine is the Facelift, so actually the FSI engine as opposed to the TFSI - but I'm guessing they carried that common issue over from one revision to the next.