3.0 tdi .... Goes flat in 5th gear only ......

[NotNormal]

The car :


Audi A6 3.0 TDi Auto Quattro 2009 facelift
CDYA engine code


The problem :


Hold a constant 2/3 's throttle - run through the gears without deviation - 1,2,3,4 all pull strong, smoothly drops into 5th and goes flat, still accelerates, then pulls strongly again in 6th


The fuel econ is also poor, 25mpg to the tank (long range 80L tank) - mpg measure correctly from fill up to fill up.


The parts it's had recently :


Complete fuel system : hpfp, lpfp, regulator, injectors x6, rails x2, link pipes, vacuum pipes, filter, filter housing, relays, entire wiring and ECU check, tank swabbed out, front to rear fuel lines flushed out, software update, adaption values reset (fully adapted again now)


Complete auto box rebuild - new oil, new transfer box oil, new rear diff oil


Turbo inlet seal replaced


Swirl flap updated and new rods fitted (both banks) (full adaption since this also)


The car has no fault codes sorted, non pending




All the work work has been carried out at main dealer Audi




Anyone got any ideas ..... We are stumped .....

 

[Jamie-S]

Why has it needed all that work?

 

[desertstorm]

How many miles has the car done ??. Seems strange that the car pulls fine in all gears except 5th yet they seemed to have decided that it may be a fuelling issue as they have replaced the entire fuel system by the looks of it.
I would be doing some data logging on the road checking boost pressures, EGT temperatures, DPF differential pressures , Pump fuel pressures etc.
Is it the gearbox that is limiting torque on the engine for some reason.

Karl.

Karl.

 

[NotNormal]

Why has it needed all that work?

fuel system was down to swarf in the system, a component breaking down - it was a recall for certain engine codes and sizes
swirl flap rods - common issue
inlet o ring - relatively common issue again, you'd see an oily buildup around the pipe at the turbo end on the compressor housing

How many miles has the car done ??. Seems strange that the car pulls fine in all gears except 5th yet they seemed to have decided that it may be a fuelling issue as they have replaced the entire fuel system by the looks of it.
I would be doing some data logging on the road checking boost pressures, EGT temperatures, DPF differential pressures , Pump fuel pressures etc.
Is it the gearbox that is limiting torque on the engine for some reason.

Karl.

Karl.

They didn't attribute the fuel problem to this - the fuel system was replaced due to a component breaking down causing swarf giving a code of low fuel pressure P0087 - any when this happens it went into limp mode

I was just clarifying what's been done ti try and be comprehensive

my cars covered 103,000 miles

DPF has been checked - both computer and physically - all ok


thanks for your input so far, food for thought .... Will investigate further ....

 

[Kenny Wadham]

Did you ever get to the bottom of this? I’m having the exact same issue.

 

[NotNormal]

Yes, I’m the mapping they have a torque limiter on 5th gear
They also have an injected quantity limit

Speak to bobby Singh on here, he will do you a map that will cure your issues

My A6 went really well

 

[Kenny Wadham]

How many miles has the car done ??. Seems strange that the car pulls fine in all gears except 5th yet they seemed to have decided that it may be a fuelling issue as they have replaced the entire fuel system by the looks of it.
I would be doing some data logging on the road checking boost pressures, EGT temperatures, DPF differential pressures , Pump fuel pressures etc.
Is it the gearbox that is limiting torque on the engine for some reason.

Karl.

Karl.

Yes, I’m the mapping they have a torque limiter on 5th gear
They also have an injected quantity limit

Speak to bobby Singh on here, he will do you a map that will cure your issues

My A6 went really well

Thanks for that. Updated the software and it did specify that there was an “improbable torque value” in 5th. Cheers for the info.

 

[minimadmotorman]

Can this be cured in an engine remap or is a gearbox map required? I've read somewhere that the box ecu limits the torque not just the engine ecu.

 

[NotNormal]

The gearbox remap helps, but the going flat in 5th is a torque limiter is in the engine ecu.
It’s not easy to find