CNHA 2.0TDI P0087 Low Fuel Pressure

[welsh_jimster]

I’ve a 2014 Audi A6 C7 Ultra black auto 2.0tdi CNHA 110k mileage

I keep getting P0087 [0x0087]
Fuel rail/system pressure too low.
What's really odd is it only happens when air temp is warm, and after you've stopped the engine for a few mins, then restart Then, only at low rpm and medium throttle. Starts first touch of the button, no black smoke , and engine runs perfectly when this isn’t happening, pulls strong with no other errors.

If you turn the car off an on again it again works fine.

Changed:
Fuel filter
high pressure pump
fuel pressure sensor (twice)
fuel pressure regulator (twice)


I've done an injector leak off test and this looked perfect. I've checked the ECU and it's not been remapped.

What I can't understand is why it only happens at 1800-2500 rpm, on medium throttle (flat out and gently is fine) and only when it's warm. It pulls like a train, on full throttle. For example if on motorway on cruise control set to 70mph, if I go up a hill it will go in limp mode, if I knock it down a gear then it's fine. It's been happening for 6 months, and is worse the warmer the ambient air temp is. I've lost a silly amount of money so far firing the parts cannon at it. Audi wanted £1800 + vat just to investigate the problem.

Has anyone goy any ideas??

[Crasher]

Where did the new HPFP come from and did you bleed the system after replacing any parts?

[mickeybo]

the problem your having at the moment is a lack of vacuum a very common fault

[Sergiu_zee]

If it s a common fault is the a common pipe that loses vacuum or is it something else? Going mad finding the leak

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[bluezie]

the problem your having at the moment is a lack of vacuum a very common fault
Perhaps you would like to elaborate what you actually mean here - lack of vacuum on a high pressure fuel system doesn't make any sense!

Does your diagnostics do live data logging? If so look at the fuel rail requested vs actual pressure and see what it's doing. It should be relatively stable for a given engine load, although will vary a lot with different loads. If it's jumping around all over the place, there's a problem.

[johnro79]

i have the same for a few years now:

5211 - Fuel Rail/System Pressure
P0087 00 [096] - Too Low
Intermittent - Not Confirmed - Tested Since Memory Clear

in my case, if i rev it up to 2500+ for a few sec, it goes into limp mode
i've managed to stop myself from getting up there ...
(only changed fuel filter and fuel rail pressure regulator as it was almost stalling at idle )