Hi all,

Thank you for taking the time to read this first of all.

I am after some advice regarding my 2018 A4 TFSI 1.4

Out of the blue a couple of days ago after pulling away from lights it became very boggy and had little to no acceleration and was idling very badly to the point it would cut out. I had it plugged in to hopefully give some indication of the issue as I had no engine management lights appear. It was found to have random misfires on all 4 cylinders. I was told I perhaps needed all 4 coil packs changing, however I believe it was a PCV issue as the likelihood of all 4 coil packs failing at the same time (new spark plugs 10k ago).

I got a mobile tech to come out for second opinion and he found the same codes and had the same opinion as me, I have replaced the non return valve hoping this would fix the issue as we had significant vacuum but the issue still remains.

At the same time of initial diagnosis at the garage I was told my clutch had almost had it which was a surprise only covering 45000 miles (12000 myself). But the second mechanic I had out also had the same opinion.

There is a significant “knock” noise coming from what I believe is the clutch/flywheel and am wondering whether the faulty flywheel/clutch could be causing the misfires.

Would this seem likely or would the flywheel being faulty/broken not cause misfires and running issues?

Appreciate any advice in advance!

Can’t comment on the clutch, whoever had the car before could have been riding it.

Regards misfires, a fuel injector on the way out could cause similar issues, such as combustion bypass or copper washer sealing has been compromised.

The knocking sound could be the DMF (dual mass flywheel) if you have one. They have a habit of disintegrating.

4 hours ago, cliffcoggin said:

The knocking sound could be the DMF (dual mass flywheel) if you have one. They have a habit of disintegrating.

I certainly do, the unknown part is if that is causing the running issues! Never straight forward 

The engine problem is unrelated a broken DMF, but would make the knock more noticable by its erratic running.

Apologies for jumping in on this, but from a simplistic viewpoint, if you agree the noise originates from the area of the clutch, then the assembly has to be dismantled for inspection with a minimum of delay.
Failure to do this could result in catastrophic failure. 

The running issue is probably not connected, but please bear in mind that no one on here has access to inspect what you describe.

Regards, 

Gareth. 
Post overlapped with Cliff’s reply. 

On 2/26/2026 at 9:55 PM, Magnet said:

Apologies for jumping in on this, but from a simplistic viewpoint, if you agree the noise originates from the area of the clutch, then the assembly has to be dismantled for inspection with a minimum of delay.
Failure to do this could result in catastrophic failure. 

The running issue is probably not connected, but please bear in mind that no one on here has access to inspect what you describe.

Regards, 

Gareth. 
Post overlapped with Cliff’s reply. 

Thanks!

Vehicle is not currently being used, even if I wanted to I could not as it wants to stall/cut out very quickly especially when put into reverse or first and attempting to move away.

The running issue definitely cannot be linked to a failing DMF? I have seen several points of view that seem to state if it was vibrating severely it could throw off the signals to the engine and cause misfires.

It is very odd, as the only codes seen are “random misfires” at all 4 cylinders. I do have someone coming to look at it so will do some more investigating. LUK clutches are on back order for at least 4 weeks worldwide for my model so I won’t be actioning that until at least then.

1 hour ago, c_s said:

The running issue definitely cannot be linked to a failing DMF? I have seen several points of view that seem to state if it was vibrating severely it could throw off the signals to the engine and cause misfires.

As Gareth mentioned, we do not have access to the vehicle, so we can only give you likely diagnoses based on experience. If you choose to believe other "points of view" you can find opinions to suit your preferences.

You mentioned some codes but did not expand on it. Was it a decent code reader or a Chinese cheapy?

2 hours ago, cliffcoggin said:

As Gareth mentioned, we do not have access to the vehicle, so we can only give you likely diagnoses based on experience. If you choose to believe other "points of view" you can find opinions to suit your preferences.

You mentioned some codes but did not expand on it. Was it a decent code reader or a Chinese cheapy?

I understand that. And in no way was that me attempting to “suit my preferences”, simply a question of it’s a possibility which as you mentioned cannot be answered. More so for curiosity than anything.

I don’t have the codes available currently, but certainly not “Chinese cheapy” either time.

16 hours ago, c_s said:

I understand that. And in no way was that me attempting to “suit my preferences”, simply a question of it’s a possibility which as you mentioned cannot be answered. More so for curiosity than anything.

I don’t have the codes available currently, but certainly not “Chinese cheapy” either time.

Hi if the flywheel has any movement in it it vibrates which in turn causes mixed signals to the crank position sensor which is mounted behind it that would cause random misfires.

Steve.