Hello all,

I have read all the semi relevant posts to this with no direct matches and plead for some input.

 

I have Skoda Octavia 2.0 tdi with the bkd engine. It was going into limp mode on the motorway under load with an overboost fault (PO234).

 

I took off the turbo and found a foreign object had entered and damaged 2 vanes and minor damage to the blade. The damage caused it to stick.

I then cleaned it and filed the vanes back to allow free movement. That left 2 vanes smaller then original, about 15% of the material on 2 of them is missing.

After that the car no longer entered limp mode and there is a massive improvement in power. The car has 130,000 miles on it and in good mechanical condition due to regular servicing.

 

 

Now the reason for this post is this - when I tow a caravan (7 meter 1300kg) it enters limp mode when on the motorways. Is it possible for a partial vane to cause overboost? I thought underboost would have been more likely.

 

This assumption is based of this video www.youtube.com/watch?v=Ppif4qC560U .  

 

All feedback will be greatly appreciated.

Does anyone know if a damaged (partial) vane that is freely moving can cause overboost on the above car?

I had the same fault code on mine. Couldn't any damage on the turbo but I ended up getting a new one :/

Which side of the turbo is damaged? Also by filing bits off I would have thought the turbo will now be seriously unbalanced and won't last very long.

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Hey man thanks for the reply.It is the exhaust side that is damaged. I guess the vanes aren't going to cause an imbalance? but the turbine blade also had minor damage near the core. There are no symptoms of imbalance and its been a couple thousand miles now.

 

It never goes into limp mode unless I tow the caravan and then it doesn't go into limp for about an hour regardless of terrain/speed.. 

 

I'd be gutted to fit a new turbo and find the code remained

is the actuator free and moving as it should to alter vane angle? If this is sticky then will cause over boost issue.

Yeah the actuator is free and possible to move back and forth just by sucking on the tube. It also holds it's spot if the tube is sealed under vacuum (ie with my tongue).

Not really sure about the accuracy of the stop screw or if it is even relevant with an overboost issue, but it hasn't been tampered with.

Getting tempted to put another turbo in although worried that a)that's not the problem or an object will enter the new turbo and damage it as well.

 

All feedback really appreciated as I don't have any experience with this but find it really interesting

VNT turbos are designed to shut off if there is no vacuum. NEVER OVERBOOST ! It is simple mechanisms to keep turbo in shape (source Robert Bosch Diesel MAnagement version V)

what diagnostic says?

 

I had similar problems and they were related to damaged MAF.

 

If there is lack of air flow (due MAF) failure and there is +-400mbar deviations of requested boost - EDC/ECU goes to limp mode

 

If I remember correctly...there suppose to be over 400mg of air at idle revs

Edited 21 January, 201610 yr by sniper29a

Thanks I will have a look at that next weekend.