Overboost P0234 A3 2.0TDI BKD 2003

[scox93]

Hi I’ve recently replaced the turbo on my A3, car seems to be running spot until I go above 3000RPM in 5th or 6th gear, then it’s goes into limp mode. Not sure if this is significant but no engine management light comes on as I’ve read normally that’s happens when it goes into limp mode. I’ve had a mate put a reader on the car comes up with fault code P0234 overboost. Car drives fine in 1st to 4th can push above 3000RPM and have it not go into limp mode. Had some advise to check if the MAF sensor is blocked I took out and inspected it looked okay but got another one on order anyway.
I was wondering whether anyone on here has had a similar issue to mine and whether I could get some advise on what to check next if replacing MAF sensor doesn’t sort it out. Cheers

 

[abmat]

was the turbo brand new? if second hand overboost could be the actuator not working properly, plus check all boost pipes are fitted correctly and there's no leaks.

If you can get access to vagcom you can read the requested boost v the actual and that can help eliminate things.

 

[DJ_26]

Very common problem on a lot of TDI engines, I've had it myself. It's most likely the variable vane mechanism stuck in the closed position due to carbon build up. Try reach the turbo (back of the engine) and see if the actuator rod is moving freely (I'm going to guess that yours will be stuck). If the actuator rod can move freely, then perhaps it is not getting enough vacuum (either a vacuum leak in the hose that goes from the vacuum solenoid block to the turbo actuator or the vacuum pump is weak and not providing enough vacuum).

If it is stuck, you have two options really:

1. Do the Mr Muscle Trick, which will strip the soot/carbon buildup in the VNT mechanism. Not too much disassembly required.
2. Get the turbo removed and sent to a turbo specialist and get them to clean out the carbon and so, free up the VNT mechanism. This is the thorough method.

 

[scox93]

was the turbo brand new? if second hand overboost could be the actuator not working properly, plus check all boost pipes are fitted correctly and there's no leaks.



If you can get access to vagcom you can read the requested boost v the actual and that can help eliminate things.

Turbo I got was new from company called turbo technics, were recommended to me by someone. Think I do know someone with vagcom but was thinking of getting it myself heard good things about it.

 

[scox93]

Very common problem on a lot of TDI engines, I've had it myself. It's most likely the variable vane mechanism stuck in the closed position due to carbon build up. Try reach the turbo (back of the engine) and see if the actuator rod is moving freely (I'm going to guess that yours will be stuck). If the actuator rod can move freely, then perhaps it is not getting enough vacuum (either a vacuum leak in the hose that goes from the vacuum solenoid block to the turbo actuator or the vacuum pump is weak and not providing enough vacuum).

If it is stuck, you have two options really:

1. Do the Mr Muscle Trick, which will strip the soot/carbon buildup in the VNT mechanism. Not too much disassembly required.
2. Get the turbo removed and sent to a turbo specialist and get them to clean out the carbon and so, free up the VNT mechanism. This is the thorough method.

Very common problem on a lot of TDI engines, I've had it myself. It's most likely the variable vane mechanism stuck in the closed position due to carbon build up. Try reach the turbo (back of the engine) and see if the actuator rod is moving freely (I'm going to guess that yours will be stuck). If the actuator rod can move freely, then perhaps it is not getting enough vacuum (either a vacuum leak in the hose that goes from the vacuum solenoid block to the turbo actuator or the vacuum pump is weak and not providing enough vacuum).

If it is stuck, you have two options really:

1. Do the Mr Muscle Trick, which will strip the soot/carbon buildup in the VNT mechanism. Not too much disassembly required.
2. Get the turbo removed and sent to a turbo specialist and get them to clean out the carbon and so, free up the VNT mechanism. This is the thorough method.

Hopefully not something on the turbo causing was new. The actuator rod was moving freely before I fitted the new turbo. I did use some turbo cleaner, Forte think it was, but that didn’t seem to make any difference. I did have someone check over the installation and give me a hand but yeah maybe leak somewhere in a pipe. Had to take quite a bit off my old turbo packed in and had all my engine oil go through intercooler.
How could you diagnose a weak vacuum pump? Cheers

 

[DJ_26]

Hopefully not something on the turbo causing was new. The actuator rod was moving freely before I fitted the new turbo. I did use some turbo cleaner, Forte think it was, but that didn’t seem to make any difference. I did have someone check over the installation and give me a hand but yeah maybe leak somewhere in a pipe. Had to take quite a bit off my old turbo packed in and had all my engine oil go through intercooler.
How could you diagnose a weak vacuum pump? Cheers

OK so that rules out the carbon build up and the actuator being stuck. A turbo from turbo technics is probably one of the best you can get in terms of quality but also in terms of correct calibration of the VNT mechanism. Try what this guy does in the video below. Simple test to see if the actuator is moving via the vacuum system:


If the actuator isn't moving fully like this via vacuum, but DOES when you get you move it physically with your fingers, then you know it is a vacuum leak or weak vacuum. You can test the vacuum pump by connecting a vacuum gauge to it and starting the engine. The pump is bolted directly to the right hand side of the intake camshaft and as the engine spins, it powers the pump creating vacuum, so the higher the engine speed the more vacuum it produces. Something like this:

 

[scox93]

OK so that rules out the carbon build up and the actuator being stuck. A turbo from turbo technics is probably one of the best you can get in terms of quality but also in terms of correct calibration of the VNT mechanism. Try what this guy does in the video below. Simple test to see if the actuator is moving via the vacuum system:


If the actuator isn't moving fully like this via vacuum, but DOES when you get you move it physically with your fingers, then you know it is a vacuum leak or weak vacuum. You can test the vacuum pump by connecting a vacuum gauge to it and starting the engine. The pump is bolted directly to the right hand side of the intake camshaft and as the engine spins, it powers the pump creating vacuum, so the higher the engine speed the more vacuum it produces. Something like this:

Yeah I was told they were the best company to go for to get the new turbo, they were very quick as well got it to me following morning.
Those videos were helpful cheers the first video I’ll be able to that check okay and I’ve got access to some vacuum gauges at work so should be able to borrow one to fit on if I need to measure how much vacuum is being produced. I changed the MAF sensor but doesn’t seem to have sorted it so will give these a try cheers