Limp mode problem - Audi A3 2004 2.0 TDI

[Slizza786]

Hi guys

Iv had this problem for a while and it's seriously dangerous for me as I'm doing daily motorway journeys.

My car goes into limp home mode and half the power is cut off. Only when i turn the car off and restart it (even as quick as straight away) the car goes back to normal. Mechanics have told me to change the turbo but I don't think it is the turbo. The cars done 102k miles but a recon turbo was fitted June 2012. One mechanic cleaned the egr valve and that did seem to help the cause quite abit but the problem is still there ONLY when i put my foot all the way down in a quick burst, if I drive at a steady speed and gradually pick the speed up the car works fine. I've changed the MAF and it makes no difference. The diagnostic test gave the error code P0234.

Anyone with similar experience or knowledge about this can possibly guide me to the right way?

Thank you in advance.

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[Crasher]

You have an over-boost problem and no matter whether the turbo was replaced eighteen months ago or eighteen days ago the MOST common reason for this is a problem with the turbo.

16618 (P0234) - Boost Pressure Regulation: Limit Exceeded (Overboost Condition)

Possible Symptoms
Malfunction Indicator Light (MIL) ON
Boost Pressure too high
Reduced Power Output

Possible Causes
Hoses incorrectly connected, disconnected, blocked or leaking
Boost Pressure Control Valve (N75) faulty
Boost Pressure Sensor (G31) faulty
Turbo Charger stuck/faulty

Possible Solutions
Check Charge Pressure Control System
Perform Output Test (to check the Turbo Charger)
Perform Basic Setting (to check the Charge Pressure Control)
Perform Pressure Test to locate Leaks
Check/Replace Boost Pressure Control Valve (N75)
Check/Replace Boost Pressure Sensor (G31)
Check/Replace Turbo Charger

[Slizza786]

Thanks crasher

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[Slizza786]

My MIL is on which gives me the indication that it's something electrical that's to do with the turbo and i believe the n75/solenoid is an electrical counterpart.

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[Crasher]

The MIL is the "Malfunction Indicator Light" and does not differentiate between an electrical and a mechanical issue BUT the engine ECU is picking up that the boost is incorrect from the MAP/IAT sensor (VW call this a "thrust sensor", I rather like that monica, it has umph!) and this is indeed electrical but then again the ECU has no other way of knowing there is a turbo over-boost issue other than if the turbine wheel came loose and ripped its way out of the housing and drilled through the ECU's bottom!

[Mitchell King]

Did you ever get this sorted I have the EXACT same issue on my 2006 A3 - the diagnostic pointed at the actuator which was replaced but did not fix the problem...

[Slizza786]

Nope. Problem is still there. The Mr muscle trick was too hard as the cat was impossible to take off and revive trick did nothing neither. Im left with the only option of changing the turbo.

[Mitchell King]

what is a good price for a replacement turbo?

[Slizza786]

Recon turbos come at around 250-300£ with labour at around 250. And new turbos at 500-900. You decide whether recon or new is ideal for you.

[Crasher]

A rebuilt turbo on a BKD is around £900 typically, fitted and including an oil and filter change.

[Slizza786]

A rebuilt turbo on a BKD is around £900 typically, fitted and including an oil and filter change.
That's the price for a brand new turbo, iv gotten that quote from Audi dealer and Audi specialists. Recon turbos are available from 250, labour from 250, oil is like 40 filter and sump plug is around 5 and labour for that is shy off 20.

[Crasher]

No, that is what you will typically pay fitted for a recon unit at a decent garage. It is five hours work to change and there are sundries like ball joint nuts, CV centre bolt, manifold gasket, manifold to head nuts and three EGR gaskets plus the V band clamp often fails and that isn't cheap for what it is.

[Slizza786]

No, that is what you will typically pay fitted for a recon unit at a decent garage. It is five hours work to change and there are sundries like ball joint nuts, CV centre bolt, manifold gasket, manifold to head nuts and three EGR gaskets plus the V band clamp often fails and that isn't cheap for what it is.
Then the Audi specialists and dealer at my end must be doing a bad job then

[Crasher]

From what I have seen in the last 33 years in the trade, more than likely...... Of two jobs in today, one Audi specialist and another Seat dealer, bloody awful work and quality right through their work-appalling!

[Slizza786]

Iv been thinking of sending my turbo off to midland turbos who have excellent experience and recommended by many. I think they will decide whether my current turbo just needs a clean or replace it with another one. Problem is I went to a dealer today who said it's most likely due to the solenoid block which has now confused me even more. I'm looking to get another scan done. Will the scan pick up an error with the solenoid if their was one?

[Crasher]

The solenoid block can play up as can the piping to/from it BUT on the BKD THE most common problem is a worn and overspeeding turbo.

[Slizza786]

The solenoid block can play up as can the piping to/from it BUT on the BKD THE most common problem is a worn and overspeeding turbo.
I'll have a look at the piping. if the block was the actual fault would this be picked up on the scan?

[Crasher]

If the block had an electrical fault then yes the ECU would detect that, if it has a vacuum leak internally then no, the fault codes you get then are the effect of the leak (if there is one), not an actual loss of vacuum message. Thinking about it, it would not have cost them a lot to have put a vacuum sensor in that box with a signal feedback wire to the ECU, it was a little stupid to go and put all the solenoids in one box but without a vacuum feedback for diagnostics.