Turbo fails at 2900 revs, main d say it is ECU, Xantia

zoics99 · Post by **zoics99** » 16 Jun 2010, 14:28

I am located in Stratford, but have just got hold of a Lexia off a friend.

I will run some diagnostics tonight, mother in-law permitting (she is visiting).

zoics99 · Post by **zoics99** » 17 Jun 2010, 08:36

Hi All, I have run the Lexia 3 over the system. The faults first highlighted -

Turbo Pressure electro valve Inlet pressure LOW - permanent fault. It appears that the pressure is 1365 milli bars, and is corrected to 2042 millibars. OCR at 88%. At 2731 revs the injection is 55mm cubed. This does not mean much to me.

I am new to the lexia and cleared the faults with a view to retest and the battery is now flat (car) so will retest tonight after a fresh run.

zoics99 · Post by **zoics99** » 21 Jun 2010, 09:10

All,

The Lexia reported this error (after i cleared the errors and took the car on a fresh run).

permanent fault, Turbo Pressure Electrovalve measured inlet pressure too low

Engine speed 2923 rpm
Injection Flow 54 mm cubed/cp
Gross inlet pressure 1318 millibars
Corrected inlet pressure 2047 millibars
Turbo Valve OCR 88%

Any ideas where to start from here? I cannot see any splits in the pipework. Could it be the intercooler, and if so how can i test?

Many Thanks,
Matt
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cachaciero · Post by **cachaciero** » 21 Jun 2010, 11:29

zoics99 wrote:All,

The Lexia reported this error (after i cleared the errors and took the car on a fresh run).

permanent fault, Turbo Pressure Electrovalve measured inlet pressure too low

Engine speed 2923 rpm
Injection Flow 54 mm cubed/cp
Gross inlet pressure 1318 millibars
Corrected inlet pressure 2047 millibars
Turbo Valve OCR 88%

Any ideas where to start from here? I cannot see any splits in the pipework. Could it be the intercooler, and if so how can i test?

Many Thanks,
Matt
[/img]

With respect you really need to understand what is going on here, I can't help because I don't even know what injection system is fitted and I don't have a Xant.
BUT I do see some contradictions here, the first is that I would not expect a low inlet pressure i.e underboosted to put the engine into LIMP mode, but I would expect an overboosted pressure to put it into LIMP mode, the second is that the rest of the data would suggest that the inlet pressure is in fact high.

So...! these re my mental questions what is the the "turbo Valve"? what does it do actually. How is turbo pressure controlled by a wastegate system or actuall control of turbine nozzle a'la C5

What pressure range does the system expect to see? what actually is gross pressure? and corrected pressure is corrected to what? is it a normalised value taking into account temperature?

Now this is my best guess

The Turbo is controlled by a waste gate system. The corrected value of pressure is over 2 Bars now I am assuming that this is a value corrected to absolute pressure which means that you have over 1 bar of boost at 2900 rpm (assuming ambient to be 1013 mBars) that sounds like a lot of boost to me. The Turbo valve (waste gate controle EV?) appears to be being driven at close to max.

In summary I suspect that the waste gate valve is not blowing of excess pressure, the ECU is driving the control EV to do this but it is not happening. Ergo either the waste gate valve is stuck closed or it is not getting any vacuum to drive it. If no vacuum then check for split vac pipes or failed Electro valve.

Quick check pipe the waste gate vac control line directly to vac pump and go drive, you should have little turbo boost but no overboost and no limp mode if the waste gate is working properly.

Caveat I don't have and never have had a Xant I may be talking rubbish.

cachaciero

zoics99 · Post by **zoics99** » 23 Jun 2010, 13:42

No respect needed. I am a novice on Citroens, and Diesels. But I love the Car.

It seems to lag power all the time. It was an almost instant change. The error and turbo light only come on under hard acceleration - when there is no power.

Thanks for all the help. I am still looking at it.