Turbo Failing - Help...please

[pete_taylor]

I've just bought an A3 1.9tdi 2001 110bhp! the problem i am having is the turbo keeps failing (i think), when i start the car its fine and has a lot of torque and gets to speed nicely, but when i hit about 3000rpm sometimes a bit more, the car kinda jults forward ( as though im hitting the redline) and then it looses all its torque! completley! in all gears - no torque! its like im driving a 1.4petrol or a 1.9 diesel with no turbo!
but when i re-start the car, its fine again, until i hit high revs!

Please can anyone help or relate to my problem? any advice would be great!

Thanks,

[docurley]

Sound like it's over boosting and dropping in to limp mode but then I would have thought it would show an engine light.

[pete_taylor]

no engine light comes up!
maybe the turbo's going! i dunno, dont know an awful lot about car engines!

how much does a new turbo cost? i think its a lot?!

[ini]

It is 95% gonna be a worn/failing mass airflow meter.

Disconnect the plug on the MAF and see if it runs better or worse.

[mandoh]

hmm is there a boost control set in the car?

[ini]

If your 110 VNT15 turbo goes into minimum boost mode (limp mode) there are several main causes for the same symptoms.

The problem will manifest usually in 3rd gear upwards, at around 3000rpm, under load (up hills or at motorway speed)

In most cases the ECU detects a 'charge pressure deviation', either 'overboost' or 'underboost' (basically, a large difference between the actual and requested boost pressure) and puts the turbo into minimum boost mode until the ignition is cycled.

This is in 95% of cases, a failed or worn MAF.

Other causes are:

Boost leak in high pressure side (you will see black smoke)

Leak or blockage in boost control tubing.

N75 boost control valve failing or blocked.

EGR valve stuck open.

VNT foils or actuator rod sticking/gummed up with crud. (make sure the rod moves on startup & when revved, move it by hand and ensure smooth operation)

VNT actuator valve diaphragm leaking or spring rusty/sticking.

Vacuum pump failing or brake assist hose leak.

Inlet manifold constricted with crud.

CAT internally blocked (CAT internals tend to form rough ball shape, that can restrict exhaust flow up hills/load etc)

Various sensor failure, mainly MAP, engine temp and fuel temp. (if you have the older style remote ECU pressure sensor, the hose to the MAP on the circuit board can fail, not applicable to your car)

Static injection timing too retarded causing underfueling.

Adaptation timing weirdness due to tuning box, remap, or sensor fault.

Fuel pump failing.

It is most likely MAF, boost control leak, or VNT mechanism needs cleaning.

If you visit a garage or the dealer with the problem, do not let them try to sell you a new turbo, your turbo is OK.

This is unfortunately a very common practice.

[pete_taylor]

ini, what you said is exactly what the car does, thanks for your replies.

Im going away shortly but will get the problem sorted afterwards and let you know what the fault was.

Thanks again for your help.

[Regina_TT]

Hey Pete,

How did you make out with your problem? I have a similar issue with my TT.

Tony

[pete_taylor]

not fixed yet, someone with the same problem also e-mailed me and he said that he replaced the MAF twice and it didnt make a difference. My cars due for a service so at the end of the month it's going in.
i'll keep you informed and if you could do the same that be great.

[hitmanaoa]

Hi, i own a 1997 110bhp audi a4 avant 1.9 tdi se, i have the same problem, but i have detected a diesel leak below the fuel pump, i've taken it to a diesel specialists and they diagnosed the leak as something to do with a 'high pressure' something or other, its only going to cost £80 + vat to fix, 1 hour labour,

now, what i wanted to get at was ini said 'fuel pump failing'
do you think this would be under the same catagory? my fuel pump doesnt need changing, but it is leaking and its going to be fixed tomorrow, if this fixes the problem i'll let u know