A6 2.0tdi ultra intermittent hesitation

[Autoquip]

Good afternoon, I am new to the forum so apologies if this is posted in the wrong section. 
 

I have an A6 avant 2.0tdi ultra with the CNHA engine and manual transmission. I have an intermittent issue which is hard to explain but I will do my best to explain what is happening. On occasion when pulling away from a junction it’s like it cuts the fuel off for a split second and then goes back to normal again, it can do this either pulling away from a junction or driving through the town at 20mph or even cruising at 50mph. It doesn’t seem to have any pattern to it and I can’t “make” it happen. Sometimes it can do it once then be ok for a few days and then do it again, it doesn’t do it every time I drive it.  I’d say it seems to be when I am feathering the throttle. I have scanned for codes and there are no trouble codes present, I have tried recording live data for various sensors but I can’t seem to find any discrepancy in the readings. To be honest I wish it would just breakdown at the roadside then it’d be easier to fault find. I have been chasing this fault for about 3 months now and I really am stumped. I don’t want to light the parts cannon as I rather diagnose faults before I replace parts but I am struggling with this one. 
 

any help appreciated 

regards

Davie

[cliffcoggin]

Transient faults like that are a devil to diagnose, and as you know, replacing parts at random could cost you many times the value of the car. I suggest you get it professionally tested as some code readers are better than others.

[Autoquip]

Hi thanks for the reply, embarrassing as it is I run my own garage! I understand about the different diagnostic equipment, I am using an up to date Autel maxysis ms909 which I use on a daily basis at my garage. The only other time I have had an issue with no fault codes was a VW Amarok, crank non start with no fault codes and it turned out to be a faulty cam sensor, however I picked that up reasonably quickly as it had no reading on live data when cranking the engine. I am still recording live data whenever I drive it, when I get to the bottom of it I will post here with what I find 

[spartacus 68]

Similar post on AudiVW forum a few years ago, but it was going into limp mode. Replaced fuel pressure regulator and fuel pressure sensor. There was no update.

I wonder if the lift pump in the fuel tank might be an issue?

[cliffcoggin]

15 hours ago, Autoquip said:

 when I get to the bottom of it I will post here with what I find 

Please do.

[Autoquip]

Spartacus I had thought about that fuel pump but couldn’t work out why it would cut the fuel for a split second. I think it would have to stop for a period of time before the engine would notice it due to the high pressure pump. However definitely worth checking out.