RS5 Fueling Issue Help

[DaytonRS5]

So I've got an issue that I've been unable to find info on. On two separate occasions now my 2014 RS5 has developed a severe misfire and then died while driving at low speeds. The circumstances: Both times have been hot days on which I was driving the car all day, spirited at times. Both times the EPC light came on while stopped at a light and then after taking off the car sputters severely and ultimately dies as I slow down. On first inspection, my local and highly trusted indy shop found a HPFP pressure switch that was not completely attached. We thought that solved this issue. However, after the second instance of the car doing the exact same thing this past sunday(8/19), the shop spent three days testing and diagnosing (Write up below). My assumption was the HPFP. However, the say they are 85% certain its the injector on cylinder 4 sticking open. This is quite an expensive repair so I just want to be as certain as possible that it's not in fact the HPFP because I've read that is an issue on some RS5's but have not read anything about faulty injectors. My car is right at 50K miles, never had a carbon clean performed and only mod is exhaust. Thoughts??

IMG_1740 (002).jpg

[croltean]

So I've got an issue that I've been unable to find info on. On two separate occasions now my 2014 RS5 has developed a severe misfire and then died while driving at low speeds. The circumstances: Both times have been hot days on which I was driving the car all day, spirited at times. Both times the EPC light came on while stopped at a light and then after taking off the car sputters severely and ultimately dies as I slow down. On first inspection, my local and highly trusted indy shop found a HPFP pressure switch that was not completely attached. We thought that solved this issue. However, after the second instance of the car doing the exact same thing this past sunday(8/19), the shop spent three days testing and diagnosing (Write up below). My assumption was the HPFP. However, the say they are 85% certain its the injector on cylinder 4 sticking open. This is quite an expensive repair so I just want to be as certain as possible that it's not in fact the HPFP because I've read that is an issue on some RS5's but have not read anything about faulty injectors. My car is right at 50K miles, never had a carbon clean performed and only mod is exhaust. Thoughts??

IMG_1740 (002).jpg

Ive been having similar issues on mine. 62k miles. I got the P0171 and P0174 codes. Today it died on me while sitting at a light. I restarted the car and all worked fine afterwards. This is be third time I’ve had this issue. I’m not getting misfires at all just system lean codes. I’ve checked my fuel trims and they’re in spec. Not sure if the in tank pump is on the go or if I have a vacuum leak somewhere.





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[JamesRS5]

I’d suspect the low pressure fuel pump going off the fault codes and your description of the fault, sounds more like fuel starvation than a leaking injector in one cylinder.

[DaytonRS5]

I’d suspect the low pressure fuel pump going off the fault codes and your description of the fault, sounds more like fuel starvation than a leaking injector in one cylinder.

That's my line of thought as well. I mean, I understand their logic; they said cylinder 4 had thousands of misfires compared to the one off misfires on the other cylinders and that an injector sticking open would cause the fuel pump codes due to the excess fuel causing pressure ratings to be thrown off. I get that but still can't find a single case of any RS5 owner having an injector issue. The other thing I forgot to mention is that when it does die it's very hard to start back up. I have to let it sit for a while and even then it acts like it doesn't want to turn over. After I let it sit for hours it starts fine. Make any sense?

[croltean]

That's my line of thought as well. I mean, I understand their logic; they said cylinder 4 had thousands of misfires compared to the one off misfires on the other cylinders and that an injector sticking open would cause the fuel pump codes due to the excess fuel causing pressure ratings to be thrown off. I get that but still can't find a single case of any RS5 owner having an injector issue. The other thing I forgot to mention is that when it does die it's very hard to start back up. I have to let it sit for a while and even then it acts like it doesn't want to turn over. After I let it sit for hours it starts fine. Make any sense?

Did you ever get to the bottom of this ?

[Reggie]

And did you try a can of BG44K? It is great for cleaning injectors. Use to be great for cleaning valves but with direction can't do it.

And that leads to my second question. Carbon Clean???

And you forgot to add lots of info like number of miles on the car.

[Ape Factory]

I can't see carbon buildup causing this and going by the codes thrown, I'd say James is right. I would replace the low pressure pump and go from there. Perhaps this is somehow causing an anomaly in one injector. It's also entirely possible both are an issue. Our injectors are used in multiple VAG cars and it's not unheard of for them to go bad, it just doesn't happen with regularity. Plus there's a very small minority of RS5 owners on this forum. Vapor lock was a problem eons ago with carbureted engines and when fuel injection was a new thing. Hard to get vapor lock with fuel pressures in the 300psi range.

With that said...if #4 is leaking bad enough that the fuel system can't keep pressure up, the injector could be the problem and the low fuel pressure the symptom. I think that'd be unlikely as the low pressure pump feeds the two high pressure pumps. Each has a pressure sensor and yet no codes stating a pressure problem with them.

Low pressure fuel pump replacement and try fuel system cleaner (Techron) for a few tanks. If the cylinder 4 injector issues don't go away, you'll need to swap that injector out. I'd just have them do a carbon clean at the same time. If you're mechanically inclined, you can do it yourself. I think someone posted a video of how to do that on this very forum. New injectors come with the combustion chamber seal already installed so that makes things easier. If it's not your daily, you can have the injectors sent out for cleaning, rebuilding where necessary and blueprinting. Or you can just replace the "bad" one.

[03TLSinCO]

… try fuel system cleaner (Techron) for a few tanks. …

Has anyone on here used Seafoam for fuel system cleaning in these cars? I've used it in my Acura & my wife's Honda, and they respond well to it. Wondering if Audis like it as well.

[Ape Factory]

Honestly the in tank solvents are not that effective short term. Can’t really hurt though. They need heavy duty solvents which aren’t legal to put in your tank.

[Ape Factory]

See this post...https://www.audizine.com/forum/showt...m-Start-Issues

[Surrey Sam]

I'd be very cautious about throwing cleaning agents into the fuel tank. The injector filter baskets are already prone to breaking up/failing and adding chemicals could further expedite that process.

[JamesRS5]

Audi has its own injector cleaner G001770A2, I run a tank of this every 6 months just because I’m not sure on the fuel quality here.

[Overbias]

Interesting thread. I am having something very similar. Either under acceleration shortly after start or randomly sitting in traffic engine will stall. When it happens under acceleration it’s terrifying! I thought it was lift pump, fuel tank pump as the first time it did it the tank was 1/4 full. But it happened last week with an almost full fuel tank. Similar to others no check engine but I am getting lean codes on both sides. I am going to replace the fuel filter this week and maybe run a bottle of BG44. I have tried Seafoam and it doesn’t seem to make any difference. Any other ideas on things to check?


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[croltean]

Interesting thread. I am having something very similar. Either under acceleration shortly after start or randomly sitting in traffic engine will stall. When it happens under acceleration it’s terrifying! I thought it was lift pump, fuel tank pump as the first time it did it the tank was 1/4 full. But it happened last week with an almost full fuel tank. Similar to others no check engine but I am getting lean codes on both sides. I am going to replace the fuel filter this week and maybe run a bottle of BG44. I have tried Seafoam and it doesn’t seem to make any difference. Any other ideas on things to check?


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The lean codes are still present on mine. Just happened again last week. So far I’ve replaced the in tank and hpfp’s.

Last week I was in traffic and noticed the engine randomly idling rough and car shut down. I restarted and all went fine from there on. When I got home I scanned the car and got the p0171 and p0174 again.

Before it happened it felt like the car was being starved of fuel.

My only assumption next is the fuel pump control module on top of the fuel tank.

Everything else in the fueling system has been changed.

The warm hard starts solved themselves after replacing the hpfp’s.

Sounds like this is a common issue creeping up on higher mileage rs5s.

Hopefully we can track it down. I love the car but it’s very frustrating not knowing what is going on.

Let me know what you come up with.




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[Ape Factory]

There seems to be no logical rhyme or reason when it comes to Audi codes. P0174 is for the transmission fluid temperature. How does that intersect with a low fuel pressure reading on one bank? Has everyone run a fuel pressure test? How bout testing the 02 sensors? While the codes are the same, the diagnostics reveal different issues and I suspect there isn't one issue which explains the symptom and codes. Frustrating.

From my own testing, the transmission gets quite hot in daily city driving, stop and go. Idling while in a drive mode (D, M or S) causes the ATF fluid to shoot up in temperature rather dramatically even in moderate temperatures. Just an observation, not sure how it'd correlate to a lean fuel condition. I'm failing to see the intersection point.

I'm failing to see how the fuel pump control module makes one bank lean. I'd do a full log using VCDS to see if the issue can be narrowed down.

[Overbias]

So, issue recurred again this morning. Here is what VCDS caught:

16811 - Fuel Trim; Bank 1
P0171 00 [100] - System Too Lean
Intermittent - Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Status: 00000001
Fault Priority: 2
Fault Frequency: 1
Mileage: 123666 km
Date: 2019.05.13
Time: 08:29:03

Engine speed: 1380.00 /min
Normed load value: 31.4 %
Vehicle speed: 42 km/h
Coolant temperature: 103 ∞C
Intake air temperature: 40 ∞C
Ambient air pressure: 1000 mbar
Voltage terminal 30: 14.347 V
Unlearning counter according OBD: 80
CAN status - engine control module-Bits 0-7: 0
CAN status - transmission control module-Bits 0-7: 0
CAN status - brake control module 1-Bits 0-7: 0
CAN status - brake control module 2-Bits 0-7: 0
selected gear-Bits 0-7: 5
Cruise control switch actuation-Bits 0-7: 0
Cruise control switch actuation-Bits 0-7: 0

I could not resolve. Car took about 5 minutes to get restarted. I had just under half a tank of gas and managed to get to refill. But that didn't solve the problem. Had to get to work so took the wifes car. I am going to check a few things tonight. Hoping new fuel filter arrives today then I can swap that out. Definitely feels like fuel starvation and when car is running its fine.

I was also running a log of Engine speed, Fuel Pressures, O2 Lambda values plus a few others (which look a little suspect, swinging from around 1 to almost 2 and then settling back to around 1, on both sides) Will do some more analysis on that data including all the failed restarts and share what I discover here.

[Overbias]

Some updates, I will post a picture of the graphed data I gathered. But basically everything was fine until the high pressure started to drop off compared to what was being requested until the stall then the high pressure flatlines. Thats the cause of the stall and inability to restart. Interestingly low pressure was maintained and exceeded the requested amount during the entire period monitored, about 20 mins. from Start to stop.

That still doesn't provide a clear cause of the loss of high pressure but that analysis coupled with the error captured above, System Too lean bank 1 leads me to suspect that it is the HPFP on bank 1. I took it off last night and the cam follower and cam shaft looks sound and clean, oil looks good (was only changed 3k miles ago) and the external of the HPFP looks fine as well.

There are multiple moving parts inside the pump though, solenoid, piston/diaphram and outlet valves so I have ordered a replacement and will see how that does.

The red area highlighted in the picture is the stall, top trace is the actual high fuel pressure and the lower trace is the requested or called for pressure. They depart just before the flatline as the high pressure starts to drop off and then the high pressure spikes high and then flatlines. My suspicion is that there is a fault in the metering solenoid in the pump. when it failed the pump continues to build pressure until it stalls out itself. Then it takes a while for that seize to relax and the car to be able to restart.

Does not rule out an electronic issue, wiring to the solenoid for instance but I am coming down on the mechanical side rather than electrical for now.

Anyone out there have additional thoughts or ideas I am totally open to them.

[Overbias]

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[croltean]

The lean codes are still present on mine. Just happened again last week. So far I’ve replaced the in tank and hpfp’s.

Last week I was in traffic and noticed the engine randomly idling rough and car shut down. I restarted and all went fine from there on. When I got home I scanned the car and got the p0171 and p0174 again.

Before it happened it felt like the car was being starved of fuel.

My only assumption next is the fuel pump control module on top of the fuel tank.

Everything else in the fueling system has been changed.

The warm hard starts solved themselves after replacing the hpfp’s.

Sounds like this is a common issue creeping up on higher mileage rs5s.

Hopefully we can track it down. I love the car but it’s very frustrating not knowing what is going on.

Let me know what you come up with.




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Hi Ape -

On mine both P0171 & P0174 come together. VCDS states that the system is running lean to both banks. Which leads me to think something is happening with the fuel pressure from the tank to the injectors. Ive already replaced the in tank fuel pump and the HPFPs. Checked fuel pressure and all checks out.

Before the codes trip, the car idles sporadically and eventually shuts down. I then restart it and runs as if nothing happened and continues to run without issue for about 2 weeks and then same issue happens again.

The only thing left to replace in my fueling system would be injectors and the fuel control module.

I wish there was a way to track it the issue down and fix it.. but no luck so far.

[croltean]

Some updates, I will post a picture of the graphed data I gathered. But basically everything was fine until the high pressure started to drop off compared to what was being requested until the stall then the high pressure flatlines. Thats the cause of the stall and inability to restart. Interestingly low pressure was maintained and exceeded the requested amount during the entire period monitored, about 20 mins. from Start to stop.

That still doesn't provide a clear cause of the loss of high pressure but that analysis coupled with the error captured above, System Too lean bank 1 leads me to suspect that it is the HPFP on bank 1. I took it off last night and the cam follower and cam shaft looks sound and clean, oil looks good (was only changed 3k miles ago) and the external of the HPFP looks fine as well.

There are multiple moving parts inside the pump though, solenoid, piston/diaphram and outlet valves so I have ordered a replacement and will see how that does.

The red area highlighted in the picture is the stall, top trace is the actual high fuel pressure and the lower trace is the requested or called for pressure. They depart just before the flatline as the high pressure starts to drop off and then the high pressure spikes high and then flatlines. My suspicion is that there is a fault in the metering solenoid in the pump. when it failed the pump continues to build pressure until it stalls out itself. Then it takes a while for that seize to relax and the car to be able to restart.

Does not rule out an electronic issue, wiring to the solenoid for instance but I am coming down on the mechanical side rather than electrical for now.

Anyone out there have additional thoughts or ideas I am totally open to them.

Thats an interesting find - Im leaning towards the HPFP on your end. When my HPFPs went my car was hard to start after it sat warm for a few hours. Now im dealing with a different fuel starvation issue even with brand new fuel pumps (low pressure and HPFPs). I think my issue may be electric.

I have a spare HPFP I can send your way if you want to try it out and see if the issue persists.. or maybe swap out your bank1 HPFP to bank2 and see if the issue follows.

[Overbias]

Oh thank you! That’s very kind. I ordered a replacement last night which should be here by the end of the week. I would agree with your diagnosis as well if the lean codes are coming from both sides it does sound like a supply issue earlier in the delivery path. I think you said you had already replaced the lift pump/filter in the fuel tank? I am going to do the filter on my car anyway. It’s done 77k miles on one filter and even though Audi state it’s a lifetime part that really only means 100k so I will consider preventative.

Odd question that I can’t find an answer to anywhere: which side on the car is bank 1? I found a reference to passenger side but want to be sure.


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[Ape Factory]

Check for vacuum leaks. You can actually log using the VCDS. Any of you have work done on the vehicle recently involving removal of major components? Heat, long term, can make some of those lines brittle. Just another idea.

[croltean]

Oh thank you! That’s very kind. I ordered a replacement last night which should be here by the end of the week. I would agree with your diagnosis as well if the lean codes are coming from both sides it does sound like a supply issue earlier in the delivery path. I think you said you had already replaced the lift pump/filter in the fuel tank? I am going to do the filter on my car anyway. It’s done 77k miles on one filter and even though Audi state it’s a lifetime part that really only means 100k so I will consider preventative.

Odd question that I can’t find an answer to anywhere: which side on the car is bank 1? I found a reference to passenger side but want to be sure.


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Yes bank 1 would be passenger side. The filer is part of the low pressure pump assembly. You may as well swap that out while you’re in there.




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[croltean]

Check for vacuum leaks. You can actually log using the VCDS. Any of you have work done on the vehicle recently involving removal of major components? Heat, long term, can make some of those lines brittle. Just another idea.

Hi Ape,

I thought the same thing that it could be a vacuum issue. I smoke tested vehicle and nothing. I then did my carbon cleaning - although it wasn’t as bad as I thought it would be. I resealed manifold with new gaskets and smoke tested as well. Nothing I could visibly see. I even went ahead and replaced both pcv valves as I read other were having issues with them leaking. No luck.

Could it be the 02’s ? Fuel pump module? Check valve ? No idea where to go next as this has all been guess works

It definitely feels like fuel starvation by the way the car behaves.

The issue is also intermittent and car runs strong when it doesn’t act up.





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[Overbias]

Updates, HPFP arrived today so after the kids were all put to bed I got to switching it out. Before I cleared any codes and adaptions from prior to the install I ran the car up to temp with the new pump. Started right up and warmed up as it usually would. When I checked the long term fuel trim it was +50% on bank 1 which means it was super lean from when the old pump was on there. I shut down, reset the codes and memories and restarted and ran a few revs and with the long term trims zeroed out they didn't move more than about +1% and the short term trims were doing their thing at +/- 3% so looks like it was a fault in the pump. (and bonus no vacuum leaks!) Low and High fuel pressure now tracks exactly as its being specified. I guess I won't know for absolutely sure until I drive it tomorrow for a while. But for now it feels good to have resolved the issue and have that validated with measurement.

I read that I should probably do a throttle calibration after the battery was disconnected for a couple of days. The throttle bodies were doing their thing after shutdown so it sounds like they do that automatically anyway. Thought anyone if thats necessary?

[Ape Factory]

I've done throttle calibration before and honestly, I don't think it changed a thing. And you're right, it'll do it on startup when you don't start the engine right away and just turn the accessory power on and again at shutdown. I don't think those clicks are the ABS module testing. It's a fairly short process so it can't hurt to do it.

[Overbias]

Getting tired of this now. Car stalled again on the way home today. Scanned it and not a single code or warning. Fuel trims all small and all fuel pressures at or slightly above the specified value. This is inline with what a few others have experienced. Replaced fuel pumps and no problems for a week or so then they return. Anyone have any ideas?


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[croltean]

Getting tired of this now. Car stalled again on the way home today. Scanned it and not a single code or warning. Fuel trims all small and all fuel pressures at or slightly above the specified value. This is inline with what a few others have experienced. Replaced fuel pumps and no problems for a week or so then they return. Anyone have any ideas?


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Still dealing with it here as well. I’m at my ends wits with this. I just ordered the fuel pump control module which should be here Friday.

My car was useless all day yesterday. It would stall out about 10 min into each drive. When I would give it gas it would stall out. It yet again triggered the p0171 and p0174, but this time the codes triggered the CEL. So it’s not getting fuel to both banks.

All pumps are new. Only thing left is the Fuel pump control module.

I’m actually thinking of dumping the car if I cannot get to the bottom of it.. it’s been nothing but unnecessary stress.


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[Overbias]

Anyone have any experience with this: 03C906051F part its described as the Manifold Pressure Sensor but interesting also 'Idle Speed Control' its located at the front of the upper intake manifold, just bolted onto the front. Its dark now and I didn't want to try and take it off but I suspect that it will be dirty from all the crankcase ventilation on cold starts so I am hoping this may be a good direction. I will know tomorrow at some point and will try and snap a picture. Its a tight squeeze but doable. I was just checking I had the right torq driver and also discovered that it was literally loose, I could move it! That could also be a source of a small vac leak I guess but not enough to cause the stalls we are seeing. So anyway check that on your car as well. To my knowledge my car has never been carbon cleaned so I am expecting it to be pretty dirty in there.

[JamesRS5]

Getting tired of this now. Car stalled again on the way home today. Scanned it and not a single code or warning. Fuel trims all small and all fuel pressures at or slightly above the specified value. This is inline with what a few others have experienced. Replaced fuel pumps and no problems for a week or so then they return. Anyone have any ideas?


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I’m going off experience of another brand car here but it was a similar symptom so worth eliminating:

The in-tank low pressure fuel pump receives its voltage through a power supply that passes through the crash relay, this is to ensure the fuel to the engine is turned off if you should have an impact. What I found on a previous car was a high resistance inside the crash switch and the strange thing was it got worse with heat. So the fuel pump draws current, the resistance within the switch combined with the current created heat, as the heat increased, as did the resistance so ultimately using a bit of Ohms law, the voltage slowly dropped as the heat increased.
Next time you get the issue, measure the voltage at the connector to the low pressure fuel pump and see where you are. I had to rig up some wires and put the multi meter on my passenger seat but it was very obvious as the journey progressed the voltage was dropping down until it would cut out.

Food for thought.

[Overbias]

I’m going off experience of another brand car here but it was a similar symptom so worth eliminating:

The in-tank low pressure fuel pump receives its voltage through a power supply that passes through the crash relay, this is to ensure the fuel to the engine is turned off if you should have an impact. What I found on a previous car was a high resistance inside the crash switch and the strange thing was it got worse with heat. So the fuel pump draws current, the resistance within the switch combined with the current created heat, as the heat increased, as did the resistance so ultimately using a bit of Ohms law, the voltage slowly dropped as the heat increased.
Next time you get the issue, measure the voltage at the connector to the low pressure fuel pump and see where you are. I had to rig up some wires and put the multi meter on my passenger seat but it was very obvious as the journey progressed the voltage was dropping down until it would cut out.

Food for thought.

Thanks James! This is great logic. I am wondering how we could check this on our car. When I was running logging on VCDS before and caught a fuel pressure problem the low pressure lift pump didn’t blink once. It was the HPFP that had a problem. Probably shouldn’t rule this out as a potential to investigate.

Today I cleaned the Manifold Pressure sensor/idle control sensor. It was dirty, no surprises there. Car is running smooth for now. Idle does actually feel a bit better and no stalls today but we will have to wait and see.




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[croltean]

New fuel pump control module arrived today. It was a 20 minute swap. A lot easier than I anticipated. Most say the fuel pump has to come out or tank has to be dropped on one end. I was able to replace it without doing either.

The module is located under the rear bench on passenger side next the the fuel pump.

It is held in place by two screws (see pictures attached). Once the screws are removed you have to carefully slide the module out.

I was able to pull slightly on the thin sheet metal around the fuel pump cut out to make just enough room for module to slide out.

Be careful when doing this as the fuel lines are plastic and can easily be broken.

Test drove the car after replacing and all checked out ok. No issues yet. Time will tell.

I’ve attached pictures with the fuel modules and location. Hopefully it can be of help to anyone else going through this.






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[Overbias]

I thought I would provide an update here on this thread. Croltean and I have been messaging back and forth comparing notes and progress. Here is what we know about this issue:

Likely not related to fuel pumps, Croltean has replaced almost the entire fuel supply system, fuel control unit, both HPFP, lift pump, filter I have replaced one HPFP and fuel duty on my car never goes above 35% even during one of its episodes.

We both get lean codes, rough idle then stalling. Then restart takes an age and smells of fuel.

We have both had our cars smoked for vacuum leaks, nothing obviously leaking.

I know he is still battling but I may have made a breakthrough. Located under the Upper Intake Manifold are a couple of fuel pressure sensors:

06J-906-051 D (Listed as G247 in Workshop manual)
06E-906-051 K

My tech went to the effort of removing them and testing and was able to find that they were intermittently faulty. So he replaced them and the car tested fine last week and yesterday so he felt confident that I could pick it up.

So far so good. I realize I may be jumping the gun here but if this does turn out to be a fix for this issue then maybe this info will help others with the same problem.

The key here is that I don't believe that the ECU can identify this problem while its happening. It just gets a wacky reading form the pressure sensor and thinks 'oh there's a low fuel pressure problem, I need to add more fuel, oh there's still a low fuel pressure problem, I need to add more fuel' hence lean codes and then rough idle and stall as the engine is then "flooded", then it takes an age to restart because... you have to burn off all the fuel and or wait for the sensor error to pass to reset the fuel trim, or do as I was doing, clear all the codes before trying to restart and the ECU supplies the default amount of fuel at startup and doesn't add to the 'already a lot of fuel' in the engine problem.

So if you can't measure the sensors with the ECU the only way to confirm if they are faulty is to get direct access to them and scope their outputs while the engine is running to understand what signals they are sending to the ECU, when my Tech did that he identified that they were sending spurious signals and that led him to want to replace them.

I will keep this thread updated if there are any further developments.

I think Croltean can chime in here as I think he's been at a Dealership and online with AOA neither I believe understand the length that you need to goto to diagnose and resolve an issue like this one.

Hope this is helpful and I would welcome discussion or input on the diagnoses, result or method.

[croltean]

I thought I would provide an update here on this thread. Croltean and I have been messaging back and forth comparing notes and progress. Here is what we know about this issue:

Likely not related to fuel pumps, Croltean has replaced almost the entire fuel supply system, fuel control unit, both HPFP, lift pump, filter I have replaced one HPFP and fuel duty on my car never goes above 35% even during one of its episodes.

We both get lean codes, rough idle then stalling. Then restart takes an age and smells of fuel.

We have both had our cars smoked for vacuum leaks, nothing obviously leaking.

I know he is still battling but I may have made a breakthrough. Located under the Upper Intake Manifold are a couple of fuel pressure sensors:

06J-906-051 D (Listed as G247 in Workshop manual)
06E-906-051 K

My tech went to the effort of removing them and testing and was able to find that they were intermittently faulty. So he replaced them and the car tested fine last week and yesterday so he felt confident that I could pick it up.

So far so good. I realize I may be jumping the gun here but if this does turn out to be a fix for this issue then maybe this info will help others with the same problem.

The key here is that I don't believe that the ECU can identify this problem while its happening. It just gets a wacky reading form the pressure sensor and thinks 'oh there's a low fuel pressure problem, I need to add more fuel, oh there's still a low fuel pressure problem, I need to add more fuel' hence lean codes and then rough idle and stall as the engine is then "flooded", then it takes an age to restart because... you have to burn off all the fuel and or wait for the sensor error to pass to reset the fuel trim, or do as I was doing, clear all the codes before trying to restart and the ECU supplies the default amount of fuel at startup and doesn't add to the 'already a lot of fuel' in the engine problem.

So if you can't measure the sensors with the ECU the only way to confirm if they are faulty is to get direct access to them and scope their outputs while the engine is running to understand what signals they are sending to the ECU, when my Tech did that he identified that they were sending spurious signals and that led him to want to replace them.

I will keep this thread updated if there are any further developments.

I think Croltean can chime in here as I think he's been at a Dealership and online with AOA neither I believe understand the length that you need to goto to diagnose and resolve an issue like this one.

Hope this is helpful and I would welcome discussion or input on the diagnoses, result or method.

As Overbias has mentioned Ive replaced nearly everything but the fuel pressure sensor (G247) located on the fuel rail. I even reached out to AOA and advised them of the issue and asked if they had any TSB's or other complaints as we are now starting to creep up in mileage on these cars. They had nothing. I told them of all the work that was done / parts replaced and provided receipts, but unfortunately they did not want to take the word of another mechanic - they wanted a certified Audi tech to confirm.

Per AOA's request they advised me to drop off my vehicle at the dealership for a diagnosis. Fast forward 8 days later and countless hours spent testing and diagnosing we still have nothing on the issue. They even called in a TAC (Technical Assistance) request as their foreman and techs could not identify the issue. When questioned on the amount of hours it would take to diagnose the answer I got was an indefinite amount and once all tests pulled out they were going to start swapping parts all at my expense.

At that point I reached out to AOA and advised them of the situation to which AOA pretty much told me good luck and I was welcome to try another dealership. Not what I wanted to hear from a company I spent a fortune with. Anyways, sorry to ramble about that but I wanted to share my AOA / Audi dealership experience - which was advised by AOA to begin with.

While at the dealership the following tests were done:

ECM Capacitive Test - All passed
TCM Test - Passed
Second Smoke Test - No leaks outside and inside the crankcase
Fuel Trim Test - All within spec
Fuel Pressure Test - all within spec
HPFP's - Tested and passed (both new)
LPFP - Tested and passed (also new)
All electrics for the fueling system - tested and passed.
The tech was then able to replicate my issue by driving the car hard. As expected the car began running lean and stalled out.

At this point I am waiting to get my car back from Audi to take back to my independent shop to replace the G247 sensor which requires the removal of the upper manifold.

Hopefully overbias put an end to this adventure as it has been very nerve racking.

I will continue to update as I make more progress.

[Ape Factory]

Croltean, I'm sure you're super frustrated, especially if it turns out to be a bad sensor. Overbias, thanks for updating and sharing your info. Much appreciated.

Once the upper intake manifold is off, it's fairly easy to get to that sensor (there's one on each fuel rail). Not sure how much wrench experience you have but the carbon cleaning thread would point you in the right direction in terms of getting the UIM off. Let me know if you need any help or diagrams.

[Overbias]

As an update to this thread. My car has been running great since getting it back from the shop. Until today. I had a rough start and idle this morning until the Secondary Air switched out then it was normal. Normal drive to work. Then this afternoon after about 20 minutes driving I could sense something was amiss. Accelerated away from a light and whack, big jolt as the engine died. It carried on for about 100 yards and then I pulled off the road and the engine died. I have started carrying my VCDS cable with me all the time now so connected it and there were only two codes. Bank 1 & 2 Lean. The long term fuel trims were at about 35% on both sides.

I reset the codes (which clears the trims) and then after a couple of retry's engine started right up and I was able to drive home. I called my shop and the car is booked in tomorrow morning for continued diagnosis.

This is all incredibly frustrating as the car has been great for two weeks. This is a familiar sequence of events, all fixed for about two weeks then the problem returns.

Just yesterday I ran a scan no codes, not one on any module. and all testing monitors passed.

If anybody has any ideas we would love to hear them.

[JamesRS5]

This happened as you were accelerating? Was it normal acceleration or a little more spirited? I’m questioning this as the suddenness of the symptoms would make me suspect an electrical fault, a loose connector or chafing wire that could be disturbed under acceleration, either by the acceleration itself or through the movement of the engine.

[Overbias]

Ha! Well it’s always a little bit more spirited we hope right?

I would say 5/10 between polite rolling away from the light and WOT as much noise as possible.

Yes I am with you on electrical fault but what I can’t then figure out is how that then converts so rough idle then stall and high long term fuel trims and lean faults.

The shop gave me an update and they spent the day troubleshooting and have not made any progress.


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[Ape Factory]

Coltrean, you mentioned all the electronics for the fuel system were tested. Does that include the low fuel pressure sensor on the back side of the engine? It's listed as G410 in the shop manual and just behind the oil filter housing. Trying to think of something that would falsify readings and cause a spike from the HPFP to compensate.

I'm assuming the high pressure fuel pumps come with new regulators. I think they call them metering valves and it's what the harness plugs into on the HPFP.

Overbuys, curious if the 02 sensors read rich before the engine dies? HPFP spikes pressure but notice there are two dips just prior, then the big spike followed by the stall and hard start (too much fuel in the combustion chamber?).

Has the PCV system been checked? Any chance the pressure control valves for crankcase pressure are bad? If you start the car and remove the breather hoses from either valve cover, should be a ton of vacuum. Maybe they've gone bad (they're the round things behind the intake manifold/Throttle bodies) and leak at higher rpm or after they heat up. Dunno. Grasping.

Vacuum system tested? Coltrean, I know you said you smoke tested. There are two vacuum chambers, one underneath the upper intake manifold and one in the cowl. Lots of hoses and solenoids are attached to the one underneath the UIM. Can test with a handheld vacuum pump.

Only other thing I can think of that goes bad around 50-70K miles would be the engine mounts. They've been known to cause issues unrelated to their function. It's also peculiar Audi lists/discusses them in the fuel injection system of the FSM.

Other than that, looking for any commonalities between the two cars might be helpful.
-Gas brand
-Engine mods?
-Any recent maintenance done prior to the problems surfacing? Carbon cleaning?

[BuyTheWarranty]

Any chance at all this is related to a faulty fuel injector? Since having my car back from my carbon clean, I’ve been dealing with multiple EPC codes and now a CEL that’s being diagnosed.

Car is back at the shop and cylinder 8 has a leaking injector causing a long hard start, EPC codes and a misfire.

Read technicians notes (potentially helpful):

Found long crank on start up. checked for DTC's and found fault P0087 .. Road test . Brought in and checked for TSB's - Found related TSB -- 2037739/3 .. for ECM update -- checked data for ECM software level - Found that it has had the update already. Road test while monituring data for high and low fuel pressue. Actual vs specified look the same when i graphed them I will need a second tech to confirm while driving.

The spoadic fault was set at 6290 RPM at full load 115 kph . it will be hard to duplicate the fault. Found that the extended crank has happened every time after I drive it. Road test to get car hot . checked data for fuel pressure 2.4mpa after drive at idle. shut engine off to moniture fue pressure in case injectors are leaking causing the long crank. found that the pressure rose to 3.2mpa then has slowly started to drop .. I would like to remove the spark plugs to inspect for fuel in cyl.

Spark Plug removal on each cylinder and inspect with Borescope. Road tested to get it hot before I removed plugs for inspection . I actually revved it past the 6200 rpm that the fault happened at and the engine cut out and the EPC light came on . I feel there are 2 issues as I don't believe injectors would cause that particular issue? Removed both air boxes. removed coils and plugs. Inspected with borescope. This time the fuel pressure after shutting off was 9.2 mpa . way higher .Inspected with scope and could not see anything abnormal. After a 10 min it came down to 7.3. Now after 30 min the pressure is almost 0. We pinched off the fuel lines going to the engine and it still fell. The drivers rear Cylinder appeared like there was a fuel mist coming off of the injector but would fog up the scope. When I cleaned it and re-checked the mist was gone.