2009 S6 / P2293 / Poor Acceleration

A6 All/ S6 All
#1

Has happened 2 times now. One day pulling out into traffic, got on the loud pedal and epc came on and went into limp mode. Cleared codes to see if I could make it come back and never did. It and didn’t happen again til today. Was in stop and go traffic for about 30 min. As soon as traffic cleared I got on it again and went into limp mode again.

What could cause this. I already replaced the fuel filter just in case. I’m wondering if I ha e a failing sensor somewhere or if it could be as bad as a failing HP fuel pump.

http://i222.photobucket.com/albums/dd45/Razgriz_10000/BE900A73-A08A-4EEC-9F77-DDB947132FD7_zpstdq90ucb.png

#2

Sorry. I thought I actually answered this.

There is a good chance your cars hpfp is not meeting request. That will put the car into limp mode quickly. The hpfp is something a few guys have seen fail you would have to log the hpfp actual vs requested to see how its performing.

Looks like you have a generic scanner not sure you will be able to log the fuel system with that.

#3

Thanks Justin.
That’s what I was leaning towards. Was just curious as I didn’t find any other topics with quite the same symptoms as mine. I do intend on getting a VAG cable setup in the next few paychecks. Christmas gifts are higher priority right now :stuck_out_tongue:

I do have an extended Engine and Powertrain warranty to 100k miles so if it does it again, I think I’ll just limp it to the dealer and let them deal with it.

#4

Having a warranty is a good move. As long as your deductible isn’t more than the work itself.

You really want to make sure you don’t clear the code in the ECU once it pops up if your going to have the warranty work done. I’m sure you knew that but I figured it better to just mention it than to not.

#5

Yeah, I only did it because I replaced the Fuel Filter as a ‘Just in case’ that was the issue. I’ve seen some nasty fuel filters before. Thanks for the suggestions :slight_smile:

#6

Somewhere in here I did a writeup about HPFP’s, it might be in the infodump thread or maybe its own thread, I forget. But basically, my car had exactly these same symptoms. Car would seem to run ok, until I really got on the throttle, and then the EPC light came on and suddenly the car wouldn’t go above about 3 or 4k rpm. I don’t believe it was actually “limp mode”, but rather it was just the engine being starved of gasoline.

The good news is that the HPFP’s are right on top of the engine, and something that anyone with a pair of wrenches can replace themselves. The bad news is that the pumps aren’t that cheap - I paid about $700 for the pair (and Audi recommends that they get replaced in pairs, even if only 1 is bad). The HPFP’s I bought online had a newer part number than the factory ones I pulled out, so I think Audi made some sort of improvement to them at some point.

I gave my old HPFP’s to JHM last year and I think they were working on making an upgrade for those, but I’m not sure if they have, check their website first before you buy them elsewhere.

#7

LOMA Motorsports makes upgraded HPFPs for our cars, but they’re like $2k for a pair I believe… Maybe next year lol

#8

JHM can sell you high flow hpfp units for about 1/4th that.

#9

Yeah I think I ended up buying OEM units last time. If I knew there was an upgrade available at the time, I probably would’ve gotten it and seen about getting custom tuning done. I guess it worked out for the best though because I just paid a little over $1k for an alternator replacement (incl labor w/ warranty), and still have to pay for whatever is needed for the S4 engine swap (maybe another $3-4k total since it’s been sitting so long), etc… sooooo I’m going to be patient on everything at this point lol… No need to jump further into the abyss than necessary for now. I’ll wait till after I’m ballin. Maybe in a year or so I can do headers and S/C etc for the S6 and maybe headers, diffs, etc the S4 whenever that gets done.

#10

Quick update.

Could not get the car to repeat the situation for the last couple of months so I had no way to investigate further.

Friday I stopped to get a to go meal and when I walked outside 15 min later, the beast would not start at all.
Videos below.
https://youtu.be/St3gUWK_hbs

I then attempted to mash the throttle to the floor and the car did run but barely.

https://youtu.be/xvlMYz4pe1k

I called a tow truck. 15 minutes later when he was about to arrive I gave it one more try and she barely ran for about 3 seconds and then the RPMs shot up and she ran like nothing happened. Cannot get it to do it again.

Given the intermittency of this issue is everyone still good with HFPFs as the likely culprit?
With the new info I just want to make sure that the HFPFs make sense still before I go spend 800-1000 on two new ones.

Thanks again for all the help everybody. >:(

#11
#12

Forgive my double post as the website does not work the greatest on mobile.

I just wanted to add that after all of this, the p2293 is STILL the only CEL.

#13

Well the videos looked like the car was running terrible.

I don’t know that the hpfp would be the only choice here. Can you log with your dig tool. That would be the most ideal thing to do. Check LPFP and HPFP when this happens to get a better idea on exactly whats happening. If you have the throttle pinned and its only making 1800rpm then there is a good case that fuel wise there is something wrong but it could also be throttle related.

IF you can log the event and see what the HPFP is at. Even without this happening I would still log it. Can you get this to happen at will or are there situations where you can make this happen.

#14

I did not have logging on when this happened, however, I did turn the scanner on and I was visually monitoring a few things with the accelerator held down and I could see that the Fuel Rail Pressure never went above 80PSI instead of the normal 500-1500PSI I’ve seen.
(That would have been useful information to include in the last post I suppose, but didn’t think about it until you mentioned logging ::slight_smile: )

This is another indicator of possible HPFP to me but the sheer random intermittentness of these issues is what makes me wonder if there’s other possibilities. If one or both HPFPs were on their way out, I don’t see how it can run fine for 3 months, not start for 30 min, and then run like normal again and I cannot get it to replicate faults. It only does it when it wants to with seemingly no correlation between faults.

I now have a gauge tapped into a fuel line under the hood and I will be watching physical pressure the next few days as I drive it to see if I can see a spot a problem with fuel pressure in real time. As said before, the problem is just getting it to act up again. I will run with my app logging as well to see what I can catch but if it wont do it again soon, I’m just going have to start replacing things. Given the interment nature of this particular issue, this may just turn into an educated guessing game, which I would like to avoid if possible.

The beast just will not miss-behave when it knows I’m watching.
(Really living up to it’s ‘Naudi’ plate)

#15

Keep in mind also that this could be the issue of the LPFP not keeping up. So that’s something to look into and the fuel gauge you have I’m thinking is going to be on the low side not the high side after the hpfp as that pressure would be impressive if you had a gauge that reads the highside. Altho you can read all of that data in a logging tool.

When was the last time you changed your fuel filter?

#16

You are correct it is on the low pressure side. I’m going to be monitoring that and see if like you said the low side could be causing any of my chaos. I changed the fuel filter in November right after I bought it. I did a basic “Service” as soon as I brought the car home. New oil and filters all round. (Fuel oil and air)

#17

Well, as I assumed, I cannot get the fault to replicate. While driving I don’t see any issues or abnormal fluctuations in low pressure fuel from my gauge. I can’t keep driving with a fuel pressure gauge sticking out from under my hood so I’m back to square one.

I have a couple of options…

  • I can continue driving it normal and wait for it to happen again. This is not ideal though because I work for a fortune 500 transportation company that requires a lot of travel and I would hate to have this happen again hundreds of miles from home.

or

  • I can start to replace suspected parts. This is also not ideal, since the issue is so intermitent, how would one know if the issue was even solved when it can take months between it acting up like this.

Y’all tell me, if this was your dilemma, what would your course of action be next? ???

#18

I think the best option for you now is to invest in a vagcom scanner. I got mine for $200, your car will throw codes even though the CEL isn’t on.
Chances are with the way your motor ran you probably have additional codes. Also you can log and troubleshoot with more accuracy.