Newbie ! - A5 3.0 TDI - Idle stutter, low fuel pressure.

Hi,

I have recently purchased an Audi A5 3.0 TDI Quattro, first Audi ownership also, apart from the 5 cylinder AEL engine in my last car (bit of fun, guess what it was ?), and have had the car a few months now. It's had a service, tyres, a good wash etc. however I am now experiencing the beginnings of an electrical or mechanical failure. The car has 77,000 miles on it, 5000 of these I have put on it since I purchased it.
I was a member of a forum for my last car, and it was invaluable. I've noticed this forum is quite active so am hoping I can discuss my thoughts with fellow members here.

The issue...

Every now and then, the car will throw a "low fuel pressure" code, shown by a flashing coil light on the dash. But nothing else. Never a high pressure code, it's always low pressure (extract from VCDS below, which I had a garage take a look for me).

When starting the car, I experience (sometimes) a stutter when the car is idling. It is pretty much exactly the same as when you start an IDI diesel engine from cold, on a cold cold morning, and the idle is really lumpy. Sometimes a stutter or two will cause the EML (coil light) to come on. Also if i look very very closely at the taco needle, I can see it visually "bopping" up and down, as if it's floating in water. You can also audibly hear the engine RPM pitch changing slightly, very similar to a big V8 with a huge cam on it if this makes sense.

This video is very very similar to what I'm experiencing, but mine will not fully stall (yet :-/)

3.0TDI stalls after starting and at idle. - YouTube

What I have seemed to notice though is this will tend to happen more when the tank is low on fuel (say a quarter of a tank) and/or when I am parked on a steep incline, either upwards or downwards facing. I have also experienced the EML light illuminating when I roll to a stop a few times too (it's an Auto so no clutch switches here).

Also, im not sure if it's just me, or a characteristic of the car, without another to compare it to, it's hard to say, but somethings telling me the pull from low rpm is a bit weak (not sure if this is physiological though), once it hit's around 1800 rpm though it pulls like crazy, but seems to run out of steam at bang on 4000rpm (yes i know theres no power up there anyway, but not sure if this is attributed to my issue).

The diesel filter has been replaced recently (first port of call for me was this) - I was told that it looked like it hadn't been changed in a long time also.

When the fuel pressure sensor (or regulator, can't remember which one) is unplugged (as in the video above also), the idle is absolutely steady.

It's going to be either the in tank lift pump which is weak or dying, the fuel pressure sensor (on the right rail i think near the centre), the fuel pressure regulator (on the left rail at the end), or the fuel metering valve on the pump itself (which some have managed to replace separately to the pump) or potentially the pump itself.

The question is, where do I start digging first ??!?!

If I buy VCDS is there any way of eliminating any of the above, I want to avoid having to replace all of the above one by one if at all possible.

Hoping that some expert opinion on here will be able to guide me.

Code:

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5211 - Fuel Rail/System Pressure
          P0087 00 [096] - Too Low
          Intermittent - Not Confirmed - Tested Since Memory Clear
            Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 2
                    Fault Frequency: 1
                    Mileage: 123367 km
                    Date: 2016.11.15
                    Time: 09:12:07
 
                    Engine speed: 1061.50 /min
                    Normed load value: 43.1 %
                    Vehicle speed: 7 km/h
                    Coolant temperature: 85 °C
                    Intake air temperature: 22 °C
                    Ambient air pressure: 1010 mbar
                    Voltage terminal 30: 14.200 V
                    Unlearning counter according OBD: 9
                    Crankshaft speed (RPM): 1061.5 /min
                    Vehicle speed: 7.40 km/h
                    Mean injection quantity: 13.53 mg/stroke
                    Fuel temperature: 29.1 °C
                    Fuel high pressure: actual: 197800 hPa
                    Rail pressure regulation: status-Bit 0: 00000101
                    Inj Crv st Inj Char Act Val 0-Bit 0: 00110100
 
5212 - Fuel Rail/System Pressure
          P0087 00 [101] - Too Low
          Not Confirmed - Tested Since Memory Clear
            Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 2
                    Fault Frequency: 1
                    Mileage: 123367 km
                    Date: 2016.11.15
                    Time: 09:12:43
 
                    Engine speed: 1260.00 /min
                    Normed load value: 99.6 %
                    Vehicle speed: 6 km/h
                    Coolant temperature: 85 °C
                    Intake air temperature: 23 °C
                    Ambient air pressure: 1010 mbar
                    Voltage terminal 30: 14.180 V
                    Unlearning counter according OBD: 14
                    Crankshaft speed (RPM): 1260.0 /min
                    Vehicle speed: 5.60 km/h
                    Mean injection quantity: 24.08 mg/stroke
                    Fuel temperature: 29.1 °C
                    Fuel high pressure: actual: 282900 hPa
                    Rail pressure regulation: status-Bit 0: 00000101
                    Inj Crv st Inj Char Act Val 0-Bit 0: 00110100
 
5215 - Fuel Rail/System Pressure
          P0087 00 [101] - Too Low
          Not Confirmed - Tested Since Memory Clear
            Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 2
                    Fault Frequency: 6
                    Mileage: 124972 km
                    Date: 2016.11.29
                    Time: 08:59:09
 
                    Engine speed: 887.50 /min
                    Normed load value: 33.7 %
                    Vehicle speed: 14 km/h
                    Coolant temperature: 83 °C
                    Intake air temperature: 15 °C
                    Ambient air pressure: 1020 mbar
                    Voltage terminal 30: 14.500 V
                    Unlearning counter according OBD: 80
                    Crankshaft speed (RPM): 676.0 /min
                    Vehicle speed: 0.00 km/h
                    Mean injection quantity: 12.98 mg/stroke
                    Fuel temperature: 37.2 °C
                    Fuel high pressure: actual: 96300 hPa
                    Rail pressure regulation: status-Bit 0: 00000101
                    Inj Crv st Inj Char Act Val 0-Bit 0: 00110100

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Year?
They don't have an in tank pump do they?

Apologies !

Early 2009 model.

They certainly do !! And a small pump next to the fuel filter also before the HPFP.

I thought it was belt driven at the front of the engine?

Quote:

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Originally Posted by rowdy-999

I thought it was belt driven at the front of the engine?

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The high pressure pump is yes. But there is also an electronic lift pump in the tank and a supplementary pump near the fuel filter as far as I am aware.

Im not familiar with the 3.0 tdi but have you considered the rail pressure regulator as well as the sensor? If the regulator isnt operating as it should, the sensor will log the fault as under pressure.... but the sensor could be fine. As shown, the fault states fuel rail/ system pressure, so hpfp pressure may not be the issue here.

Quote:

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Originally Posted by Alan02

Im not familiar with the 3.0 tdi but have you considered the rail pressure regulator as well as the sensor? If the regulator isnt operating as it should, the sensor will log the fault as under pressure.... but the sensor could be fine. As shown, the fault states fuel rail/ system pressure, so hpfp pressure may not be the issue here.

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Indeed I have

Quote:

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Originally Posted by a5qtro

the fuel pressure regulator (on the left rail at the end)

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Is there any way of testing these various sensors, perhaps via VCDS or testing the resistance at the connections etc. Or is the only way to replace one, and see if the fault remains, i.e. method of elimination.

Various threads on other forums and here regarding this kind of issue with the V6 TDI seem to all end up at the HPFP, specifically the metering valve, which cannot be purchased on it's own, at least not from VW or Audi. What the exact issue with the valve is, i am unsure.

Hi Mate. I have an Audi A4 3.0 TDi with the exact same illness as described in this post. You dont have an update of what it turned out to be at the end?

Quote:

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Originally Posted by Daddycassanova

Hi Mate. I have an Audi A4 3.0 TDi with the exact same illness as described in this post. You dont have an update of what it turned out to be at the end?

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It's not mine is it? Unfortunately not, I ended up selling the car. Not because of this issue though. I replaced several sensors but ended up settling on the basis that it was possibly a dodgy injector.

be interested in this as having same issue but when at full throttle