Power Loss & P2293 - Fuel Pressure Regulator Valve (N276): Mechanical Malfunction

Ok... having trawled through the US Audi forums (I defected to the US around 5 years ago) trying to find a solution to my ongoing issues, I stumbled upon this forum. It seemed like there was a bit more knowledge flying around so figured I might get some better responses here.

Here's a brief history:

Car is a 2006 A4 2.0T with 120,000 miles, no mods
Experienced some power loss under hard acceleration which felt like a fuel cutout
Was getting a P2933 - Fuel Pressure Regulator Valve (N276): Mechanical Malfunction code.
Also getting a B310 code.
The dealer changed the high pressure fuel pump, camshaft and follower under an extended warranty
The B310 went away but the power loss and P2933 came back
The dealer diagnosed the in-tank fuel pump (working too hard)
Changed fuel filiter and the in-tank LP fuel pump
No change to the symptoms.

Below is a VCDS log from before the LP filter and pump change. Below that is a link to a longer log (.xls) after the LP fuel filter and in-tank pump change.You can see the HP pressure drops and corresponding values fro engine speed, LP pressure, throttle angle, LP pump, etc.

To me it looks like the problem is on the HP side, i.e. the LP fuel readings seem fine but the HP readings drop from over 100bar down to single figures. Despite these logs, both the dealership and forum posters keep suggesting the LP side. I can see how a problem with the LP feed would affect the HP feed but if anything, the LP value is at its highest when the HP is failing...!!!

Any suggestions what might be causing these issues?

http://www.legoheads.com/Log2.jpg
http://www.legoheads.com/Log1.jpg


http://www.legoheads.com/VCDSx1.xls

You dont say why the Dealer changed the Pump etc. What was the diagnosis for them to be suspect? Worn ? Maybe the Fuel rail pressure regulator or sensor?

There is a VAG TSB / TPI where the 2.0 TFSI engine can get the following DTC logged:

P2293 control valve for fuel pressure, mechanical complaint

P1093 fuel pressure control, below limit

P0087 fuel rail/system pressure too low

Symptoms described as engine warning light on, often in connection with erratic engine operation or poor performance in the upper load range.

This is due to wear of the drive cam for the high pressure pump, the necessary pump piston lift is not reached causing rail pressure fluctuations. The wear on the cam often leads to wear of the bucket tappet base which may disintegrate.

What is your engine code?

Below are the original codes that prompted the dealer to carry out the TSB on the HPFP, follower and cam. Ignore the first one; I forgot to replug following an oil change... :Blush2:

Following this work, the P2293 has returned but rarely puts the CEL on, only once after frequent multiple occurrences. And like I said, changing the LP pump and filter made no difference either. I did see a thread related to a pressure relief valve that bleeds of fuel from the HP side when it exceeds either 116? or 126? bar depending on the car model. I also saw something regarding the HP fuel pressure sensor, which if faulty could fool the ECU into thinking pressure is low and causing it to cut power (similar limp to mode). If this is the case, it seems like it only fails when HP pressure is at or near its maximum.

I was wondering if either of these could likely be at fault in my case. In the later case, I may try to run the VCDS logger again and add the lambda value to see if it's genuine fuel cut or the ECU sticking its nose in...

Sunday,22,June,2014,08:53:07:46862
VCDS Version: Release 10.6.0

Address 01: Engine Labels: 06F-907-115-AXX.lbl
Control Module Part Number: 8E0 910 115 M HW: 8E0 907 115 D
Component and/or Version: 2.0l R4/4V TFSI 0070
Software Coding: 0104010A190F0120
Work Shop Code: WSC 08144 444 84095
VCID: 2B5E05F2B55F2644
3 Faults Found

005491 - Left Engine Mount Solenoid Valve (N144): Open Circuit
P1573 - 004 - No Signal/Communication - Intermittent
Freeze Frame
Fault Status: 00100100
Fault Priority: 0
Fault Frequency: 1
Mileage: 187418 km
Time Indication: 0

Freeze Frame
RPM: 740 /min
Load: 21.2 %
Speed: 0.0 km/h
Temperature: 69.0°C
Temperature: 49.0°C
Absolute Pres.: 1000.0 mbar
Voltage: 13.589 V

012555 - Low Pressure Fuel regulation: Fuel Pressure Outside Specification
P310B - 004 - No Signal/Communication - Intermittent - MIL ON
Freeze Frame
Fault Status: 10100100
Fault Priority: 0
Fault Frequency: 6
Mileage: 187483 km
Time Indication: 0

Freeze Frame
RPM: 994 /min
Load: 71.0 %
Speed: 6.0 km/h
Temperature: 33.0°C
Temperature: 33.0°C
Absolute Pres.: 1000.0 mbar
Voltage: 14.097 V

008851 - Fuel Pressure Regulator Valve (N276): Mechanical Malfunction
P2293 - 002 - Lower Limit Exceeded - Intermittent
Freeze Frame
Fault Status: 00100010
Fault Priority: 0
Fault Frequency: 1
Mileage: 187538 km
Time Indication: 0

Freeze Frame
RPM: 3113 /min
Load: 9.4 %
Speed: 90.0 km/h
Temperature: 88.0°C
Temperature: 34.0°C
Absolute Pres.: 990.0 mbar
Voltage: 13.716 V


Readiness: 0000 0000

This is going to require a diagnosis by someone who can look at the logs and determine what may cause this issue. And possibly someone who might suggest other parameters that it may be useful to log.

After doing some additional research, I ran some more logs after adding in the lambda value. As you can see below, the lambda value suggests the power loss may be a direct result of genuine fuel starvation and not (as I wondered) as a result of the ECU killing power due to an erroneous (low) HP fuel sensor reading. The only other time you see such a lean reading is when the throttle is almost closed on overrun and no fuel is being thrown in. That said, the ECU is definitely reducing the throttle when compared to the actual pedal position (not in the log) so it may also shut off the injectors due to the low fuel pressure...? Who knows...? It's hard to draw a proper conclusion without a better working knowledge of the system.

It's also worth mentioning, that the issue is intermittent and symptoms aren't necessarily consistent, i.e. the problem may or may not occur given seemingly identical circumstances. In addition, sometime the car jerks whereas other times it feels more like a limiter has been applied.

http://www.legoheads.com/lambda1.png
http://www.legoheads.com/lambda2.png

Still limping along with this issue. I've scoured the forums and seen many suggestions for some of my symptoms. I've seen a few people change the LP fuel sensor (thrust sensor), which has sorted their problems. In my case though, it seems that the LP side isn't the problem, the HP side is.

I've been wondering if the HP fuel sensor may be at fault? My thinking being that the apparent fuel cut is simply the engine going into "limp mode" upon detection of apparent low HP fuel reading?

Alternatively, I'm wondering if the fuel pressure relief valve is cracking open and pushing all the fuel back to the LP rail, effectively robbing the injectors of the pressure they need and slightly raising the LP rail fuel pressure (as seen in the logs)?

I could just spend the money and throw parts at it, and believe me, at this stage of the game I'm tempted to do just that. Problem is, how much money do I waste before I drop a burning rag in the tank...?

Just a thought, but is there a measuring block for checking the fuel temperature?
If the ECU is seeing high fuel temp it may dump pressure from the rail to compensate for expansion. We all know how bad VW temp sensors can be.

Just a thought.

Jim.

Firstly a drop in rail pressure due to blockage needs to be eliminated so you will find there is valve under the inlet manifold on the fuel rail, remove it and replace it as this has a gauze filter which blocks.

https://www.google.co.uk/search?q=tf...%3B1600%3B1200

Try to use a fuel pressure tester to calculate accurate pressure.

Quote:

---

Originally Posted by a8 tech

Firstly a drop in rail pressure due to blockage needs to be eliminated so you will find there is valve under the inlet manifold on the fuel rail, remove it and replace it as this has a gauze filter which blocks.

Try to use a fuel pressure tester to calculate accurate pressure.

---

From what I understand, this valve is a regulator which returns fuel from the HP rail to the LP side. If this was blocked then it would fail to return fuel to the LP side potentially resulting in excessive pressure on the HP rail, not a drop in pressure. The only way I see this valve being at fault is that it is opening (possibly due to excessive pressure) but opening too much and for too long, effectively dumping all the pressure to the LP side instead of "regulating the HP rail fuel pressure. Am I missing something?

Based on a mix of ease of task, probability of part at fault and price of replacement part, I've decided that the HP fuel sensor shall be the first item to replaced...

Fuel Pressure Sensor, 2.0T (0261545050)

Next will be the FRV... and then the LP fuel pressure sensor.