A7 2012 3.0L BiTDI - very rough idle/vibration when stationary

[memgrubb]

Hi there - new member here, first thread.

Engine code CGQB.
'62 Plate A7 2012 3.0L BiTDI S Line

I have done a little searching on here but as thread title states, I've got a really rough idle when stationary e.g. on start before moving off and stopping, in traffic or at lights.

- No warning lights on dash
- The car has been mapped slightly (not aggressively)
- More pronounced as engine gets warmer. It's the same in PRN or D
- Exhaust note seems to have changed to a popping/whomping noise since the problem has occurred. No other noises than this.


The car pulls and shifts gear fine EXCEPT there is a very very brief vibration when accelerating just before the downshift like the car is labouring. This is when going round a roundabout or on the motorway before an overtake.
As soon as slowing down for lights as the car comes to a stop, the roughness/vibration starts again.

I have seen this could be related to, in order of likelihood and cost
Engine mounts
Injectors
Timing chain or timing chain tensioners (expensive)

I have it booked in a diesel specialist in Cheshire tomorrow 20/02/23.
I have told them pretty much what I have written here - is there anything else I should be aware of?

Cheers.

[AK88]

Hi,

what was the outcome from the specialists on this?

[memgrubb]

Failed injector #1

Cost just over £1,000 including labour, using OEM parts. The car had also been remapped by a previous owner, so I got them to map it back to factory.

I could have got it cheaper with a reconditioned or aftermarket injector.

Fortunately I had a 3rd party warranty which covered the lions share, so I went for an original injector and just paid the difference myself, around £300.