Turbo Issue

davidjay85 said:

Hi,

So recently my car (Audi A4 2.0 TDI) was suffering from Limp mode and puffs of smoke coming out of the exhaust.

This turned out to be a faulty EGR valve that was not closing properly. I have replaced the EGR valve and the car is now back to normal again....almost.

It now drives normally for about 10 mins and then goes into Limp mode, no smoke this time. (restarting the engine resets the limp mode) I had the codes read and got P0234 -Turbo boost limit exceeded.

I'm hoping the turbo isn't broken (it feels like its working before it goes into Limp).

My (wishful) thinking is that the EGR valve failure (and smoke) could have resulted in the Turbo getting dirty and it just needs a clean.

Can anyone advise on this, or had similar experience?

Thanks,

Dave

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Hi there i have the sort of problem it started a while ago doing around 60mph then all of a sudden now power eml on pulled over turned off the bk on fine no problem eml off. Then fine for a week same thing happened had car scaned with vds and i got the overboost code i google and asked so was told could be n75 valve sticky vains on turbo or its on way out i also read someone with the problem found that flushing the system with redex cured his problem so i let my tank get very low put a whole bottle redex in and nothing for around 3 months the back again ive tried redex again but hasnt work also sprayed a can of egr turbo clean into air intake which lasted about a month the limp mode again no other faults so now looking for a garage to have a look at the turbo there is a guiide to clean the stucky vains but im no mechanic so wouldnt try myself.
So there is temp fix but id say in long run get your turbo checked when you can.

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Sticky wastegate possibly; check wastegate opens smoothly and doesn't catch/stick.

As for vnt vanes, apparently removing the middle pipe off the N75 valve and sucking on it will move the vanes, they should move and stop suddenly.

I have removed the middle vacuum line of the boost pressure control valve (N75) and sucked on it.

The actuator (for the VNT vanes, right?) then moves easily and clearly stops with an audible stopping sound (not mushy resistance).

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