Help !! Running issues , need advice

[kwalker705]

My RS6 has developed a little issue and wanted some advice from the more "in the know" members on how to check what could be wrong and hopefully fix the problem.

Cars been faultless of late, but yesterday while on a long motorway journey while cruising along the car suddenly lost power from the engine and wouldnt take much throttle. I pulled to the road side, stopped and the car idled fine. It would rev with no problems. I got going again and under light throttle the car is fine, as soon as it gets a bit of load on the engine the car starts holding back again.

Managed to get into a service station and checked everything over and couldnt see or find any issues visually. Decided to set off again and just take it easy. I noticed that my average fuel economy started to decrease as time went on. After a few hours more driving the emmisions control light came on. I hit a bumpy stretch of road and all of a sudden the car would take throttle again and was running with no problems. Got to my destination and parked the car up overnight. Started it this morning and the issue was back again.

Managed to get it onto a generic scanner this afternoon and got the following codes

P0171 - lean bank 1
P0174 - lean bank 2

From some digging online many threads say MAF sensor or vac leak. Is there any way to check more in depth for what might be wrong..either with or without VAG-com. Any help would be greatly appreciated

[Shoppinit]

Either you suddenly developed a big leak or your fuel pump just died. The fact that it sorted itself out points to latter.

See what your air mass flow is at idle with the Vagcom to eliminate. It's harder to check your fuel pressure.

Try driving it with the fuel filler cap off (briefly) to see if that helps. If it does you could be looking at a tank venting issue.

[kwalker705]

Wouldn't the car fail to start and run if it's a fuel pump failure ??

[Shoppinit]

Depends on the failure. Plus there are 2 fuel pumps. Could be the lifter.

[shadyraven]

Pumps and/or filter... good place to start.

[kwalker705]

A lot of money to change them in the hope of fixing the problem. Need to look into how to check them if that's possible at all

[Shoppinit]

Make sure the pump voltage increases upon cranking. The fuel pump module has 2 voltage outputs depending on demand.

Check all the electrical connections to the fuel pumps.

Do a fuel pressure test. Bit of a pain, but no more.

When's the last time the filter was replaced?

Did you try without the filler cap?

[kwalker705]

Filter was done about 5k miles ago. Not had a chance to check with the fuel cap off yet.

Might not be able to get at it till next weekend. But will try and get it onto Vagcom as well next weekend

I hate to be an askhole when everyone is giving advice.. but could the N75 valve cause this if it wasn't controlling boost properly and causing the boost to spike or be too high

[kwalker705]

Issue resolved now.

Shoppinnit hit the nail on the head 100%. external transfer pump had failed. Connector plug was pretty messed up too.

Car is also now sold and with a very happy new owner.

[Ajc]

Glad you've sorted it Keith and the car is off to a new owner .
Howe you getting on with the track project bud ? .is it battle ready yet ? .
Al

[kwalker705]

Glad you've sorted it Keith and the car is off to a new owner .
Howe you getting on with the track project bud ? .is it battle ready yet ? .
Al

car came back with 736bhp..... took it off the road for winter to tie up some small jobs and then sent it for paint a month ago . Excited to have it back soon and get it abused in the dry weather.

[Ajc]

Jesus dude , I bet that's a handful on the road . Plenty of good roads up your way to play on mind