Misfire on heavy acceleration

[dob2023]

Your expert advice would be appreciated with this one.

 

First of all the car: 2014 Octavia 1.4TSI DSG 44k miles with full main dealer service history on the 12month service interval.  The car has been problem free since new and all servicing completed as required (with dealer).

 

The car has now experienced a problem.  On heavy acceleration (lets call it kick down) the car starts to bump and bounce along. Briefly get the engine management light (orange) on and the EPC light (orange) flashes on / off then stays on.   It wont accelerate unless full throttle and plenty of time (only needed to do this to get off the motorway).    Stopping and with the car on tick over the engine is struggling with the revs blipping up and down.  Engine start stop system inoperable error comes up.

 

I turn the engine off, take key out.  Put key back in and turn engine on.  Everything is back to normal.  I can drive again without issue, no lights, until kick down and then the above happens again.

 

I plugged in a code reader and got the following pending (but not stored) fault codes on "7E8 Engine" (whatever that means):

P300 - Random/Multiple cylinder misfire

P303 - Cylinder 3 misfire

P301 - Cylinder 1 misfire

P299 - Turbocharger A underboost condition

 

It is in with the usual main dealer.  They have replicated the issue and found that it is happening across all four cylinders.  They have replaced the rubber seals at the top of the spark plugs (as they were showing signs of wear) but made no difference.  They have checked spark plugs (replaced about 18months ago) incase they were faulty and also the coil pack.   They have checked other things but I am unsure what they are.  They have now contacted Skoda technical for advice.  BTW I have to say that the dealer in my experience is very good.

 

While they are checking with Skoda I thought I would check for your expertise please as I am sure that one / some of you have come across this before.   

 

Many thanks for your time and comments. 

[Ootohere]

Really checking with Skoda Technical about a 9 year old Euro 5 1.4 TSI.    I think there is kidology right there. 

 

The Dealer might be very good, bit what about the Tech / Fitter or Master Tech? 

 

The posts in the Tech section you have are interesting but not everyone will see them.

 

An actual Tech / Mechanic might be along that can help you as this is their job and they will have seen plenty of 1.4 TSI's with issues over the past decade or more and likely do not need to BS customers / owners.

 

Edited 16 May, 2023 by toot

[dob2023]

Toot, thanks for the reply, not sure on your advice on the issue here?

[Ootohere]

I gave no advice.

 

Those that work on them all the time will be along.

 

Replacing the rubbers but the coils being ok is interesting.

The Spark plugs replaced 18 months ago but checked again is interesting.  

 

You will hopefully get advice here from someone that has not got the car in front of them.   

Probably more help than from whoever has the car right there and supposedly needs help from another remote source at Skoda / VW Technical. 

[Breezy_Pete]

It's not clear from your opening post whether the coil pack(s) (not sure if individual ones or one for all cylinders on your engine) was replaced?

You seem to say it was 'checked'.

 

Engine code always useful, check boot build sticker if you don't know what it is.

[dob2023]

@Breezy_Pete the coil pack was swapped to a new one with no difference.

 

As I dont have the car at the moment I am unable to check the engine code.  Is there another way to find it out?

[Breezy_Pete]

3 or 4 letters on the front of engine number on V5c certificate.

[dob2023]

@Breezy_Pete thankyou - CHPA

[Breezy_Pete]

Well done.

Interestingly the wiring info I'm looking at for CHPA shows four individual pencil-type coil packs, one on each spark plug.

So that begs the question, which did they change, any?, all?

 

Given the other (underboost) fault code, and the multiple random misfires, it's tempting to think the cause may be lean mixture rather than electrical/electronic.

 

Edited 17 May, 2023 by Breezy_Pete

[Ootohere]

Once the dealership figures it out then try some E5 if running it on E10.

 

http://briskoda.net/forums/topic/513284-epc-engine-light-with-horrible-gear-changes-dsg200

 

 

[dob2023]

@Breezy_Pete - thankyou for the investigation, I had assumed one coil, I will ask the question.

 

In somewhat relation to your question and also related to @toot then I first found it happen after I filled up at Morrisons from an empty tank and I assumed that it was either crud from the bottom of the cars tank or poor fuel.  I put in some Wynns Fuel Injector Cleaner into the full tank, did a long drive, a few days later topped the rest of the tank up with Shell V-Power.  This has not made any difference.  Now this could be that the issue was there before (wifes car and she doesnt kick down much) and the refueling and issue are a coincidence. 

 

@Breezy_Pete your question does play on my mind. Is this something to do mix, air flow ?  When driving normally everything is fine.  After the issue and a car restart everything is fine.  When a burst of fuel is required is when the issue kicks in.....

 

Thanks both for your continued thoughts.

 

[Ootohere]

Surely no crud in the bottom of your cars tank and you do have a filter.

Morrisions or any other place is not feeding crud from their tank through the filters to the pumps then through the filter in the pump.

2023 we are on now & these are modern filling stations. 

Edited 18 May, 2023 by toot

[IonC]

Hi,

I have exctly the same problem.

Did you manage to fix it?

 

Thanks,

Ion

[-nebojsa-]

@IonC Hello, I was randomly browsing briskoda, and have seen this topic. I may help you, I had a similar issue, juddering/misfire at heavy acceleration  and on higher rpms. Also fuel consumption increased. DTC popped up on VCDS, but none on the dash. All of them were misfire related, BUT seems to be caused by 2nd exhaust sensor (commonly referred as lambda probe). After exhaust sensor replacement problem went away, consumption went down-normalized. Used BOSCH 0 258 030 221 (my Octavia is 1,2 tsi CJZA), but check if it fits your 1,4 TSI as I don't know which code is used in Australia.

Worth mentioning that i've changed the spark plugs at the same time as a precaution since the car was obviously running rich due to faulty sensor.