EPC/Engine lights + limp mode

A6 All/ S6 All
#1

Hey guys, I’m about to leave for Spain for 4 days so unfortunately I don’t have time to mess with it til tuesday, but a problem just came up in my 2007 S6…

I drove my car to work this morning, no problems at all. Went out for lunch, came back, still no problems at all. But when I left work in the evening, Immediately after hitting the gas pedal pulling out of the parking lot, the revs won’t go any higher than about 4k rpm, and the EPC and Engine lights come on. Oddly, the car runs fine below 4k rpm, If I don’t apply more than 50% throttle then it drives perfectly normally. If I mash the gas pedal, forget about it, car slows down instead of speeding up. Driving using a light foot, car was able to get up to 80mph no problem as long as I didn’t push the throttle too far.

When I got home, I pulled the terminal off the battery and let it sit for about 5 minutes, then connected it. I turned the ignition to “on” without starting the engine, mashed the throttle to the floor about 10 times, turned the ignition back to “off”, and then proceeded to start the engine. All looked good (and dash lights were gone) until I pushed the gas pedal past 50%, and suddenly it’s not letting me go over 4k again and the lights came back on.

So before I take it to the shop next week, I’m hoping to get a little input from you guys so I can walk in armed with at least a little information. Or maybe someone knows something I can check on my own first?

What I’ve read online seems to point to a problem with either the ECU, wiring, or a sensor.

Unfortunately I can’t get any VAG-COM readings til I got to the shop.

#2

ok a few things. Were there flashing lights on the dash. Like did your EPC light flash or your check engine light flash.

If you couldnt get over 4k and you couldnt use more then part throttle that would make me lean in the direction of throttle body failure or speed sensor failure. But if you said you could get to 80 that might not be the speed sensor. Generally when the RPMs are limited thats a communication issue.

The thing that sucks is that a vag com read would probably put you right where you needed to be. I doubt that just pulling the cables cleared any soft codes. So I think you are going to want them to pull the data from the ECU and then please check back with us to let us know what the codes were that came up

#3

Neither light was flashing. The EPC light comes on all the time now after I rev over 4k, but the engine light only comes on sometimes.

I’ve continued reading online, and it does seem like a possible throttle body issue or maybe just a MAF sensor problem. On tuesday I’ll take it to the shop for a code read.

#4

If it cant go over 4k and its just the EPC its going to be communication related. Mostlikely the throttle body. The MAF wouldnt cause that to happen. You would get a EPC and traction control light if the MAF was going bad. It shouldnt be anything too serious. When you get back please let us know

#5

Just got back from the shop. First of all, impressed with the new shop, they had a line of high-end Audi’s in the parking lots and in the shop, including S4’s and an S7, so clearly a lot of Audi owners trust them. Anyways, they gave me a free diagnosis, and came back with the conclusion that it is an issue with one (or both) of the high-pressure fuel pumps. Sounds about right, and it might explain why my car sometimes smells like unburnt gasoline. I’m taking it in again on Thursday so they can remove and test the fuel pumps and check the cam chain followers that I guess could be the problem as well, said it should only take around 2 hours. Then, we order parts and wait… Hopefully that’s the only problem, but it seems reasonable. They said the gas flow is fine at low RPM, but drops to almost nothing as the RPM’s increase, which is definitely what it feels like it’s doing when I’m driving it.

#6

Shop went through everything, checked the cams and everything, and the problem is definitely the high-pressure fuel pumps. Sounds like one of them has probably been out for a while, and the other one was working overtime to pick up the slack, and burned itself out. Shop quoted me $490 each for the pumps, $250 for labor to replace them…

It seems that the 5.2 engine fuel pumps (part #07L127026A) are garbage - Audi has since discontinued them, and replaced them with a newer (and more expensive!) version (part #07L127026AD). Anyways, I found them online for $377 each, and since they’re surprisingly easy to access (pop the hood, both of them are right there on top of everything), I’m just going to do it myself and save $500.

#7

Is there anything I need to know about replacing the fuel pumps, or is it pretty much just a “take off the old one, put on the new one” sort of thing? Any gaskets, sealant, or anything like that I need to deal with?

Once the pumps arrive (next week hopefully) and I perform the swap, I’ll do a full writeup about this problem (and solution) to add to the infodump.

#8

Good find on all this. I have not hear anything on the pumps being bad so it will be interesting to see the difference.

Pulling them off is stright forward. If you want pulll out the cam follower and make sure thats ok too. It sits right under the pump you will see it when you pull off the pumps

#9

The shop inspected the cam followers and says they’re good to go, but I’ll take a look for my own curiosity as well.

I’m definitely curious to see if there is any performance gain from all this. Sadly, I don’t have any benchmark numbers from before the repair, so I’ll just have to judge it by how fast the car feels, lol. Honestly I’m not expecting much difference, although maybe low-rpm throttle response will be better, because that’s always seemed unnecessarily sluggish to me (I always chalked it up to the trans). Anyways, enough speculation on my end for now, I’ll give it a go next week and hopefully put together some good info for the rest of you! Thanks for your help Justincredible!

#10

Problem solved! New high-pressure fuel pumps was the answer. I just posted a writeup in the Infodump!

#11

I noted in my original post that my car interior has always had an occasional scent of gasoline in it after I’ve been parked for a few hours. I haven’t noticed the scent since I changed the fuel pumps, so I suspect it was due to a leak in one or both of the old ones.

#12

Also, engine power seems to be about the same as before the fuel pumps failed, so the new pumps don’t seem to change much in that regard.

#13

It sounds like most fuel related stories. Glad to hear its fixed. Thanks for keeping us posted