Audi A4 B7 3.0 TDI fuel pressure mystery

[mihtu]

Hello!

I have a A4 B7 3.0 TDI quattro with a manual 6 speed gearbox. I have a problem with common rail pressure dropping under the norm for 2-3 seconds and it causes the engine shudders. The problem appears when engine is 70+ degrees warm. When the engine is under 70 degrees Celsius it does not shudder.
Engine shudders appear when revving the engine and then letting it go to idle and when doing a complete stop from driving. Some times theres no shudders at all. It drops a little under the norm of the rail pressure and it shudders for 2-3 seconds and then it goes back to normal. Engine idles good and while revving theres no shudders.

I have changed the fuel filter when i bought the car half a year ago, the fuel filter was not very expensive one.
I have visited a well known multi-brand car service center in my city and they found that its either a fuel pump pressure regulating valve or the rail pressure relief valve. They also suggested that it might be the remap that does it, but I dont believe it because it did shudder before remap also.
I changed the fuel pump pressure regulating valve but the shudders are still there. After changing the regulating valve I dont have high hopes. There is no fault codes to be seen either.

Tomorrow I am going to swap Rail pressure relief valve ( Bosch 057130764N ) from my friends 2,7tdi and see if it makes a difference.


All help is welcome.

Mihtu

[p0isin]

Have any data logs of low pressure fuel system pressure or pump duty cycle? Also high pressure system rail pressure?

[mihtu]

I have no data log of low pressure system pressure or pump duty cycle.
To be honest I dont know where to get or look at them. I can get my hands on vcds to check them though.

[mihtu]

I had my car looked at by professional mechanics that specialize to diesel engines and they say that its the injectors. I have changed 4 out of 6 earlier because they were bad. Now, a month after the install two old injectors gave up. On sunday I went for a short drive, in 3rd gear I noticed a little jolt at 2000rpm. Sped down and gave it a little go and at the 2000rpm the car started furiousli shudder. With all gears 3-4-5-6 it did that. Two times i managed to stall the engine. When i arrived to my destination I hooked up VAS and there was no fault codes.

Karla Auto mechanics told me that everything else was fine but some injectors must be faulty. I think i ruined the old ones with coding them again. I have read that you should not code old injectors again if you reinstall them.