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 I have an Audi A3 2.0 Tdi 2004 62000miles.

I have read most forums regards issues of overboost/limp modes, however:

First instance was it went into limp mode with orange engine light, on scan error code P0234 Over boost. Turned off engine light and deleted error code.

Garage told me due to car sitting in garage for a few months during Cov-19 isolation, more than likely carbon on vanes and advised to treat fuel with 2 bottles of Forte Advanced diesel treatment to clean system.

However the car runs fine turbo appears ok, until I hit 8o mph, whereas it loses power down to 6o mph and no turbo kicking in, there is no engine warning light and on scan shows no errors.

However on stopping turning engine off then restarting engine all runs fine again until taking it to 80 MPH on the speedo.

I have taken the car to the high revs to red on speedo to just under 80 MPH and it runs ok, occasionally it kicks out some smoke which hopefully is the system getting cleaned. But I cannot understand why the car keeps losing power {{limp mode} but no engine light or error code?

Anyone advise where to start looking at possible reasons, as my garage has also scanned and found nothing, just said keep running it and give it the gun to clean out the system?

Anybody have any advise to what the problem is?

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Hi, sorry am I missing the point here, how the hell would the turbine vanes soot up if the car has been idle for months its not like a chain smoker that was sitting in an armchair all through the lockdown.

I think it has more to do with either the MAP/Boost sensor on the intake manifold side or the Oxygen sensor on the exhaust, in view of the age of the car the MAP sensor would be the first port of call as these for a car of your age are relatively cheap, sensors should be changed about every four years regardless of milage as age is the main factor with failure, most sensors are high heat resistant plastic and especially the MAP which has a plastic pressure membrane inside it but even this will degrade over time when it is dealing with hot air and gas and sends an implausible signal to the engine management system which will throw up a light and put it into limp mode.

have never been a fan of aggressive fuel system cleaners as invariably they will loosen dirt in the system which then heads for the injectors, not good, if you use a spray down the air intake cleaner to clean your turbine this heats the fuel up and as it comes into the engine via induction and goes no where near the internals of the injectors and cleans the intended part and nothing else.

Steve.

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A faulty battery can cause those sort of problems, even if the alternator is putting out a good current. Is the engine turning slowly when cranking the starter? Do you have to keep the battery topped up on a mains charger? Is the acid level up to the mark?

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Fair enough, it must be something else.

The advice from your garage is utter nonsense. Soot can not be created or deposited in a non running engine.

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On 4/3/2021 at 12:27 PM, Stevey Y said:

Hi, sorry am I missing the point here, how the hell would the turbine vanes soot up if the car has been idle for months its not like a chain smoker that was sitting in an armchair all through the lockdown.

I think it has more to do with either the MAP/Boost sensor on the intake manifold side or the Oxygen sensor on the exhaust, in view of the age of the car the MAP sensor would be the first port of call as these for a car of your age are relatively cheap, sensors should be changed about every four years regardless of milage as age is the main factor with failure, most sensors are high heat resistant plastic and especially the MAP which has a plastic pressure membrane inside it but even this will degrade over time when it is dealing with hot air and gas and sends an implausible signal to the engine management system which will throw up a light and put it into limp mode.

have never been a fan of aggressive fuel system cleaners as invariably they will loosen dirt in the system which then heads for the injectors, not good, if you use a spray down the air intake cleaner to clean your turbine this heats the fuel up and as it comes into the engine via induction and goes no where near the internals of the injectors and cleans the intended part and nothing else.

Steve.

Hi Steve,

Thanks for your advice, however being a newbie not too sure if I am looking at the correct MAP/Boost sensor on the intake manifold side, as you said in your reply.  I only have an HAYNES manual to go by.

May I ask if the attached picture from the manual is the boost sensor in question white pointer, pointing at it.

Also is it easily accessible to disconnect and remove, to identify the product number to buy a new one to fit. As there appears to be many types or can you recommend one such as Bosch from eucarparts or replace with an Audi one?

Much appreciate if you can advise me on this DIY or would I be better asking a garage to replace it with a new sensor?

Pete

 

1432003634_SensorA32.0tdi2004.thumb.jpg.6289813e8a030f5c84c7dd63d8f273a3.jpg

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Hi sorry for the late reply, the picture you supplied is indeed a boost sensor, if yours looks like that you are in, either way scrub the dirt off and get the part number then go fishing on eBay plumb in the Audi part number and it will give a good range of choices this way it will be a lot cheaper than the thieving scrotes at Audi or Eurocarparts.

I am pretty sure that this item is plug in and play and won't need coding, I will check, if you have a problem deciphering which number is the part code either post a picture of your cleaned part so I can see the numbers or email me the VIN for your vehicle and I can't the number off of my system, Do not remove the old part until you have a new one as the pipes can be awkward to remove because they are crusty and may need persuading with a bit of hot soapy water

Steve.

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hello i have the same problem with my 2l tdi it doesn't fully go into limp mode but the boost cuts right out on hills and when going over 60 in high revs. the turbo also had a loud squeal, I used a turbo cleaner in the tank but that hasn't made much of a difference. iv aslo been told it could be the turbo actuator but that seams to be running fine. also been told putting Mr Muscle into the egr. does anyone have an idea on what it could be?

 

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1 hour ago, tyla said:

hello i have the same problem with my 2l tdi it doesn't fully go into limp mode but the boost cuts right out on hills and when going over 60 in high revs. the turbo also had a loud squeal, I used a turbo cleaner in the tank but that hasn't made much of a difference. iv aslo been told it could be the turbo actuator but that seams to be running fine. also been told putting Mr Muscle into the egr. does anyone have an idea on what it could be?

 

Hi I don't think putting Mr Muscle into the EGR will do it any favours, thats an old MK3 mondeo trick plus you have to drill a hole in the vane casing to put the stuff in and then tap the hole fitting the correct size screw and heatproof washer, you mentioned that the Turbine was squealing thats not good and a sure sign its about to go terminal, if you are getting boost at slower speed the actuator is probably ok but the Turbo itself is not.

I think you are probably looking at a new Turbo unless you have any EML lit up in which case I would get the codes read before spending any money.

Regards Steve.

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21 hours ago, tyla said:

We did a diagnostic and it said turbo was  over boosting   

Hi now we are getting somewhere it is possible the boost pressure sensor is defective but the Turbo whining is never good, what code did you come up with?, its hard to diagnose a problem from your armchair if you don't have ALL the information available.

Regards Steve.

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