problems this morning

[skinso]

don't fancy a rebuilt turbo. not sure on what to do next

[gupsterg]

Before trying the turbo... have read of this suggestion...

Whilst cruising around the web I found this video...



The large cog which is removed showing worn teeth on the lower cog would mean egr valve is defaulting to close...

I double checked this by reading SSP 412 Audi 2.0L 125kw TDI Engine with Pump Injection System on page 19 you will see what is in the video...

2 Faults Found:
001027 - EGR Valve (N18)
P0403 - 000 - Malfunction - Intermittent

Fault Frequency: 169

* 001032 - EGR Potentiometer (G212)
* P0408 - 000 - Signal too High - Intermittent

Fault Frequency: 15

Freeze Frame:
*Mass Air / Rev.: 335.0 mg/str
*Mass Air / Rev.: 440.0 mg/str

By looking at another's egr valve fault video/SSP/your data IMO I would run the VCDS output test in module 1 to actuate the EGR valve...

The EGR valve on the 2.0 TDi is spring loaded so if cog fail it will be permanently closed...

What I learnt when my air mass reading were out the turbo forces air into intercoolers, this process makes dense air (high air mass) when egr open warmer air (less dense) mix with it to create right air mass (density) of air... if the valve is closed air mass reading will be too high...

I believe the * Mass Air reading is what your ECU want... * is actual reading of Mass Air...

[skinso]

cheers gup ur an audi support tech

[gupsterg]

Only a meddling owner mate ...

[skinso]

today I undone the plug coming from the airbox not sure on the name, air mass sensor? took it for a spin and car works fine. can I drive with this unplugged until I get it sorted?

[skinso]

[gupsterg]

I have and am doing the same... on mine (3.0 TDi) with MAF disconnected exhaust gas recirculation (EGR) system is switched off... engine ECU start using engine speed & mass air pressure sensor (MAP) to calculate mass air flow (MAF)... car does run richer on fuel though...

Some of the & I have been having for the past months has all been down to the EGR system having faults ...

In my case the faults with EGR have make me think car had had it ...

I would assume the 2.0 TDi function the same way... I will try to check hopefully another can comment/advise...

[skinso]

gup where does that leave me? what needs fixed/replaced?

[gupsterg]

2 Faults Found:
001027 - EGR Valve (N18)
P0403 - 000 - Malfunction - Intermittent
Fault Frequency: 169

001032 - EGR Potentiometer (G212)
P0408 - 000 - Signal too High - Intermittent
Fault Frequency: 15

Mass Air / Rev.: 335.0 mg/str
Mass Air / Rev.: 440.0 mg/str

The above red text numbers need to match... they are not...

When you are disconnecting MAF the car starts defaulting to preset values for mass air flow, so it ignores the red values in a way...

If your car start behaving after MAF disconnected then IMO you must check the EGR system thoroughly...

Lets say your EGR valve is functioning once you test it with VCDS then the EGR cooler can blocked or the cooling flap, etc could have issues...

Please read thoroughly the SSP412 Audi 2.0l 125 kW TDI Engine with Pump Injection System

The exhaust gas is first sent through a EGR cooler, there is a flap which is actuated to decide if it need cooling... then EGR gas get to the valve, then valve opens and closes to release as much or as little EG is needed...

Also read SSP358 Hot-Film Air-Mass Meter HFM 6

The above SSP will explain a lot about air mass, etc ... I would assume if MAF sensor was faulty it would have appeared in log, it must be checkable via MVB's in VCDS to see if that is fine...

*** Update ***

The amount of exhaust gas recirculated is determined from the air mass meter signal.

Page 19 of SSP412 Audi 2.0l 125 kW TDI Engine with Pump Injection System

With diesel engines, the signals are used to control:
- the exhaust gas recirculation quantity and
- the injection time.

Page 8 of SSP358 Hot-Film Air-Mass Meter HFM 6

Signal use diesel engine

The measured values are required by the engine control unit to calculate the exhaust gas recirculation quantity and the injection quantity.

Effects of signal failure diesel engine

If the air-mass meter fails, the engine control unit will use a substitute air-mass model that is stored in the engine control unit for this case.

Page 14 of SSP358 Hot-Film Air-Mass Meter HFM 6

I'm pretty sure after reading above you are switching off EGR system by removing harness from MAF... car is then defaulting to fixed values and then functioning well...

I did swap MAF's on mine and in the end it was/is the EGR which has been causing ...

[skinso]

Did u get sorted gup? I went and bought a new airflow meter and fitted it today and plugged it back in and problem is still there so thats £130 down the tubes