My daughters A3 started chugging at idle, louder higher frequency at revs. Extra loud when removing the EGR pipe or the air box. I was expecting to see some loose intercooler/air/vac pipe, but couldn’t find any, and no changes when squeezing/wiggling pipes. No engine fault codes thrown with my ODB11 :(

The black box (valves?) that all the vacuum lines connect into has a high frequency whine, but assume that may be normal?

Any ideas what to look for before I give up and take to local garage? Cheers 

Hi possibly an injector seal check round the injectors for oily tar like crud.

Steve.

Will do, cheers 

I’ve never had cause to investigate injectors on a vw tdi. I’ve removed the rocker cover, but everything is very oily and I can’t see any obvious crud.

Obviously I’ll wipe it off, and check more carefully, but should any blow-by from injectors be very obvious, or would I need to remove injectors to see it? I presume I cannot run engine with the rocker cover off. 

Im a bit nervous of how hard it might to prove to remove injectors, and then replace them properly...

11 minutes ago, Kester said:

I’ve never had cause to investigate injectors on a vw tdi. I’ve removed the rocker cover, but everything is very oily and I can’t see any obvious crud.

Obviously I’ll wipe it off, and check more carefully, but should any blow-by from injectors be very obvious, or would I need to remove injectors to see it? I presume I cannot run engine with the rocker cover off. 

Im a bit nervous of how hard it might to prove to remove injectors, and then replace them properly...

Hi by rocker cover do you mean the plastic noise shield?, if so clean the oil to and run the engine whilst looking at the injectors hold your hand flat just above each injector in turn if one is blowing you will feel the pressure and heat so be careful, don't try removing an injector unless you have to as they require a tightening sequence which you will need a torque wrench for the tightening of the foot that holds the injector down, this dictates the crush pressure on the new seal and above all a clean seat and surrounding area of the injector is an absolute must, I would say something is amiss as the whole injector area should be dry, also look at the injector feed pipe unions for diesel leaks as this will cause uneven running due to the fuel pressure being lost at the offending injector.

Steve.

Thanks for all this advice. 
The black plastic rocker cover has like 16 captive bolts and an oil seal, and the oil filler cap. So I assume it keeps the top cams bathed in oil, and I can’t run engine with this off. 
I’ll try and clean up the oil and see if I can see any blow-by residue. But I fear any problem won’t be obvious 😞

Garage reckons it’s the camshaft, or hole in valve lifters. May be more than the car is worth. 
or I can take the plunge and try and do it myself 🤣

Hello Kester,

Neither of these components would seem to me to be terribly difficult to isolate as a cause - although ‘hole in a valve lifter’ would appear to be unusual, as really would be undetectable camshaft issues. 
As you say, as a 16 year old car, the repair bill will likely represent the value of the car, and I guess it’s decision time as whether you have had you money’s worth out of it and are prepared to move on, or if it’s been a faithful servant on which it’s worth further investment. 
Since we are talking diesel? here, why don’t you find yourself a local diesel specialist to canvas for opinion? 
Kind regards,

Gareth.