2009 3.0tdi lumpy idle.

[Mechcanico Lee]

Mmmm couple of things come to mind

1 If its exhaust valve sticking due to carbon deposits up the stem of the valve this could be treated chemically , you need someone with a BG flushing machine or similar .
You use chemical to treat the inlet system via a 'fogging nozzle ' which inturn will clean the combustion area and on the valve overlap period it will be able to work at the valve stems ...... definatly worth a go , they rattle like a good un running on the stuff but it can work wonders for carbon cleaning

If its a burnt valve ......yes head off only will fix that .

2 Is this engine on hydraulic followers or hydraulic buckets .... Burnybubbles will know about this
If it is on hydraulic followers the relief valve in the bucket/follower can gum up and stick closed so it cannot reliieve its self and in some cases it lift the valve off its seat causing loss of compression .

With this fault get two of the Forte hydraulic additive chemicals , do an oil and filter change first and put the additives in with the new oil .......had great results with this stuff especially with hydraulic issues where you get the clack clack noise from them .

[harvmiester17]

Couldn't agree more, we stock the full range of Forte products and have had surprising results with them. If it is a hydraulic follower then use there engine flush for an extended period, drain the oil and leave the engine to cool. Then refill with fresh oil, oil filter and Forte top end treatment. It make take a few miles for a result but it's definitely worth a try before removing the head.
I've used this method on a lot of VAG cars and cured a lot of valve train problems. Good luck

[legacy4cam]

Thanks for the suggestions.
I don't think its a hydraulic issue, as the follower is clearly free of the camshaft when the valve should be in the closed position , as seen by the other exhaust valve. No discernible valve train noise difference from bank to bank, or cylinder to cylinder when the trusty screwdriver to ear is applied.

So that leaves us with possible a carbon build up on the stem , as I think it closes once the revs come up and the cylinder compression rises quicker than the leaking valve can relieve it. SO chemical cleaning may be an option.

What is the BG machine mentioned ? Is it something I can do at home, or can anyone suggest someone in central Scotland who is known and trusted? I'm a bit sceptical of these things normally, but I am prepared to try something.

I cannot see it being a bent valve, as that would require some contact or hydraulic issue, neither of which there is any evidence of.

[Mechcanico Lee]

Have a look at this demonstration with Frank Massey .

Where abouts are you in Scotland? will find out from my Top Techs garage forum who is closest to you .

https://www.youtube.com/watch?v=w4ABTo42tKA

[Burnzybubbles]

There's no buckets but the followers are solid with a hole in them for the oil gallery into the head, the rocker is also a roller rocker so it considerably helps cam wear

One thing to bear in mind just in case, is the cams can not be reinstalled without the correct tooling, you need a special locking set that hold the cam sprocket as it has a backlash compensation ring, and then you put them onto a jig and fit another tool that holds both cams at tdc ready to be dropped into the head, I dare say with a bit of common sense and some imagination you could make up some stuff to fit them but the VAG tools to do it are around £500 iirc and why I opted for a replacement head instead of repearing my own.

[brasiliangringo]

You can physically measure injector return flow and total fuel return flow at idle. You will need tolerances from the workshop manual or Bentley. Im sure you can find something on google. Tbh with you find unless you have the kit its probably more cost efficient to fine a BOSCH diesel specialist, most garages will farm out stuff like this to guys who spend all day doing injector type diagnosis. Just find a decent one.

[legacy4cam]

Sorry for silence on this, I have been away for a week or so, car has been with Audi for assessment of fault....

I'll report the outcome ASAP.

[legacy4cam]

Okay, so Audi UK were hopeless on phone when asked for "someone technical" to speak to about what may have caused the issue with my car.

Hamilton Audi however were much more interested, and took car in for diagnosis, confirmed a low compression in one cylinder, and my car is now repaired. The report suggests an inlet seat has become "misaligned", although I believe this should say exhaust ... unless the valves are so close together that the exhaust valve was fouled by the inlet..however I was unable to view the parts, and didn't want to push the matter in the circumstances.

It has had a new cylinder head fitted, with associated gaskets etc and fluids replaced. Suffice to say Audi made an exceptionally generous contribution to the repair.
I am mightily surprised and delighted , despite knowing the car is impeccably maintained and completely genuine, it is over 6 yrs old, with only partial Audi history (albeit having 7 recorded services in 69000 miles, and being sold to me as Approved Used with non Audi stamps in book at 2 yrs old) . I had no prior experience of Audi Hamilton, (new branch) but will certainly endeavour to put some business that way in the future.
I am still disappointed that the fault developed, and am undecided whether the car will remain the "keeper" I had in mind for it, but fingers crossed it is at least back to good health and will be used daily for a month or so to ensure it is in fact fully cured.

Thanks to all who offered suggestions and support.
I do have an intermittent parking sensor fault to address now....anyone got phantom black front outer sensor lying about..??

Cheers, Iain.

[Mechcanico Lee]

Wow ! thats a good result to get warranty on the age of the car , valve has become miss aligned ......mmmm not so sure how that happens , apart form it getting a clonk off a piston .
Good news its all sorted out anyhow .

[snapdragon]

Ouch, glad you got it fixed and even better to get a large portion contribution.