Audi A6 2.5tdi 2003 Allroad loss of power

**dguy01** · 18-02-2010,09:31 PM

I have just experienced a loss of power when accelerating and going over 3000 revs, the car feels like it is misfiring I have no engine fault lights on.

The car was serviced about 3 weeks ago and has done aout 94000 miles new cam belt at 80000.

I filled up with diesel from Sainsburys Watford dome roundabout two days ago and have done about 100 miles since then, so I am concerned it was faulty fuel.

Any ideas would be appreciated....

**fjtwelve** · 18-02-2010,09:48 PM

Could be a number of things, any other symptoms?

**dguy01** · 18-02-2010,10:12 PM

No other symptoms that I can think of, it just seems to be when i am accelerating hard that it starts to lose power/misfire...

Thanks.

**Kyojitsu** · 19-02-2010,04:10 PM

One possible cause is a faulty needle lift sensor. It basically acts as a control loop for when fuel is injected into the cylinders and can be checked using diagnostics. It's called a G80 fault. As I understand it, symptoms include sluggishness, misfiring and a lack of power. My Allroad has this logged as an intermittent fault but no obvious symptoms, so it could be a wiring problem rather than the sensor being faulty. A new one is about £260 plus fitting.

Your car sounds like it's got a problem with either fuelling or air flow. The fuel pump or possibly mass air flow sensors could be faulty. Best bet is get a diagnostic done.

**Kyojitsu** · 19-02-2010,04:12 PM

PS I notice you say it happens only when accelerating hard so perhaps it's related to the kickdown control?

**Camb-Tech** · 19-02-2010,07:48 PM

It might be your fuel pump.

The fuel pump needs to advance the fuel timing under full throttle, if the advance diaphragm is shot then it causes miss fires and rough running. It may run fine under light loads and cruising.

You need to get a scan done ASAP.

**luklawecki** · 20-02-2010,12:26 AM

Do u see smoke in your rear view mirror when loosing power...?

**bartboy** · 22-02-2010,07:40 PM

This sounds like the exact fault mine has, If accelerating hard I get about three gear changes before loss of power requiring lifting off the accelerator for a few seconds before power is restored. Daignosis showed an N75 fault which I replaced this made no difference. The diagnostic tool now shows "inlet pressure outside tolerance" My local garage (not Audi but very reputable) seem baffled and want the car in for two days to find the fault. they have already done a pressure test and ruled out a collapsed cat. They are now talking about sticking vanes on the turbo. If you find out what the fault on yours is please let me know and I shall do the same when mine is rectified. I've noted the other threads about it and will suggest these fixes to the garage. At the minute it is no problem pottering around but dangerous when trying to overtake. Oh! and I'm only getting 18mpg pottering around town which seems a bit low but may be connected to the problem.
cheers,

Yep. as feared turbo vanes sticking and turbo had to be renewed, goes great now, better gearchanges and mpg, expensive though.

**Oldfart** · 22-02-2010,10:24 PM

There is a small hose which runs from the exhaust, near the turbo, to the ECU. Apparently they collapse and cause power loss.

That said I cannot trace it on my 1.9 red eye so if you could give me any guidance it would be appreciated.

**Shaka1976** · 24-02-2010,11:34 PM

I had a similar fault which after getting VAG COM'd led me to the N75 which appeared to be working. I then noticed the actuator rod on the turbo wasn't moving even though the N75 was. It then became apparent the diaphragm had split. So replaced it with a unit from 1.9TDi (as nobody would sell me a 2.5TDi unit) and now works fine.