2008 - 2.0 TSI - P0300

[Skymera]

Hi all,

I've recently joined (see my introduction thread!)

So I've bought my first Scirocco. It's a slightly older model being a 58 plate but it's still a nice car. It had a slightly misfire / hesitation when I test drove it but took a gamble as the car was pretty reasonably priced.

I'm still new to VW / TSI engines so reaching out here for some expert advice on where to go next!

The car
2008 Scirocco GT
2.0 TSI
100k miles
Partial service history
Has only done 1,300miles in 18 months

Fault Codes
P0300 - Random / multiple cylinder misfire detected
P0302 - Cylinder 2 misfire
P0303 - Cylinder 3 misfire
P0304 - Cylinder 4 misfire

Symptoms
Hesitation at low RPM when accelerating. To mitigate this I'm usually a gear lower than I should be to keep the RPM higher, about 2-2.5k. WOT feels okay but a strong cat smell suggests all fuel is not being burnt.
Occasional misfire at idle. Though I will say idle is generally very smooth. It doesn't fluctuate much when monitoring with my OBD reader.
Strong smell from the cat after a period of WOT. I'm assuming this is unburnt fuel from the misfire.
More noticeable when engine is cold

Progress so far
I have replaced all 4 pencil ignition coils this morning and did a quick 3mile drive on my lunch break and I'd like to say there was some improvement but the car was still warm from my drive in so I can't reliably say if there has been an improvement. I have cleared the codes since fitting them and will drive it home tonight and report back.
I have 4 NGK Platinum spark plugs on the way. I checked the ones fitted currently and they looked used, but okay. They're Bosch branded and can't tell which model so unsure if the gap is correct.

What next?
Im seeing a lot of people talking about carbon buildup on the intakes for these TSIs and being on 100k is it reasonable to expect this to be an issue? Do the symptoms above sound like carbon?

TIA

[Skymera]

Just an update.

I have replaced the spark plugs with new NGK Platinum and this morning have replaced all four ignition coils with new Bosch ones.

The misfire seems to have disappeared when the engine is warm or it's so subtle that I don't notice but driving when cold is still a bit jerky.

I also bought an OBD2 code reader and can confirm that no fault codes are being generated

[Skymera]

I am booking the car in for a new timing chain, tensioners and water pump, just for peace of mind really since I've read some horror stories on the tensioners failing!

Going to speak to the garage about whether they can diagnose the misfiring whilst they're working on the car.

I'm aware this thread is slowly turning into a blog / chronology of my antics so I'll expand a little on my plans.

Once the car is running sweet I'll be fitting new BC coilovers and a DCC deleter kit. The Scirocco carts me down the M4 and back 50miles a day so I'm keeping it reasonably sensible (I've had a daily that was laying frame before, not fun) I just need some lows and then I'll be fitting these that I managed to get hold of over lockdown



Hopefully I can get them fitted before winter sets in.

[Hrsprs]

My situation is pretty similar to yours. I've recently bought 2008 Scirocco 2.0 TSI as well, but mine has 46k miles.

I am booking the car in for a new timing chain, tensioners and water pump, just for peace of mind really since I've read some horror stories on the tensioners failing!

Would you mind sharing some more info when you get it done? I would like to know the price estimate for this job, since mine hasn't had the tensioner replaced either and I don't really want to risk it.

Nice rims by the way.

[Skymera]

Not much of an update. I've been living with the intermittent misfire for almost 2,000 miles now, it's so minor I barely notice it.

I have the car booked in at a VW specialist local to me on the 16th. £72 to diagnose the fault(s) seems reasonable to me. The outcome of the diagnostic will determine if I repair the vehicle or chalk this up as a loss and sell it.

The wheels have been sat in my hallway for over 3 months!!

[blower]

With this mileage and this engine (2.0TSI), and your symptoms of misfire, particularly when cold and on low RPM......i'd say its probably from intake valve carbon build up.

If this engine has never been decoked by media blasting or manual mechnical cleaning with the intake manifold off - then it will be coked up to hell and have all the above symptoms.
Having ruled out sparks and coils, and with the misfires not on just one cylinder...this is more than likely the issue.

[Skymera]

With this mileage and this engine (2.0TSI), and your symptoms of misfire, particularly when cold and on low RPM......i'd say its probably from intake valve carbon build up.

If this engine has never been decoked by media blasting or manual mechnical cleaning with the intake manifold off - then it will be coked up to hell and have all the above symptoms.
Having ruled out sparks and coils, and with the misfires not on just one cylinder...this is more than likely the issue.

Thanks! You may be right
I have it booked into a VW specialist on the 16th who will be taking a look for me.