Long Term Xantia HDi problem, advice appreciated...

[Sulla]

Hi Guys

New user on this forum but I have owned a Xantia HDi since 2006. Its the 110 version and I love it to bits, such a vastly underated car in my opinion and I love the fuel economy you can get from this engine compared to the previous TDi (I owned one of them too until I slammed it into the back of a Toyota Avensis).

It has done 130k and has a full service history from new, gets a full service every year and has been very well looked after mechanically, no expense spared etc.

It has however had one problem since I have owned the car which no one seems to have an answer for, perhaps you guys will have an idea?

When it gets to the summer months and the temp is warm it sometimes goes into 'limp homemode' when I change gear to accelerate (usually 4th). I can have the pedal mashed full into the carpet and I will get no increase in revs, power or accceleration. I have to lift off and feather the accelerator pedal until the turbo catches and everything is OK again. It will also happen when cruising on the motorway at 85 mph, I will put the foot down and get no response in power. It only happens at 85 though and if I lift off the accelerator and allow the speed to drop to 82 I can then put my foot back down, the turbo catches and off I fly.

It used to really annoy me when I first got the car and until I cottoned on it caused a few 'brown trousers' episodes when trying to overtake only to find I had no power. Now I am used to it and can tell if the throttle wwill take or not and I have adjusted my driving to suit.

I would like to get the problem sorted though if anyone has any ideas?

Cheers

Sulla

Oh and anyone got any idea where I could pick up a new set of HDi hubs or alloys, they seem very hard to find!

[DickieG]

The best thing to do is to get your car connected up to a Lexia to see what faults are recorded in order to avoid spending money or time potentially searching in vain.

[thorter]

It is certainly worth trying Lexia diagnosis, assuming there is a fault stored.

My 110HDI Xantia had a problem that could be related. Above 30C ambient, after getting fully hot, then being parked for perhaps 20 minutes, it would go into limp home mode when restarted. After a few miles, if turned off and immediately restarted, it then worked normally after that.

By accident when working behind the engine, I found the vacuum connection to the turbo waste gate capsule was a loose fit, though it had never come off by itself. After making a secure seal by sleeving over the connection with a short length of larger tube, the problem has not recurred.

The ECU sets up the vacuum for the required level of turbo boost by mark to space modulating the electrovalve. Presumably a slight leak can upset this, and also presumably, the ECU monitors the actual boost pressure against the demand, and a sufficient discrepancy triggers limp home.

Fred

[citroenxm]

The electro valves work in a reverse way.. The waste gate needs the Vaccum APPLIED from idle to spin up.. The vacuum CLOSES the wastegate then when turbo boost pressure set by the ECU it then switches the Electro Valve (Sitting up be the Came belt cover, by drivers side sphere) to exhaust so the wastegate opens.... if the wastegate stays colsed and you get over boost the ECU goes in to LIMP mode, but only Softly... By softly I mean it is resetable by ignition off...

Thorter, Switching off the ignition resets the Over boost record hence getting full power.. The elctro valve was not switching to close the waste gate, OR as you found the vacuum leak.

Sulla, it sounds like you have the opposite problem and the elcectro valve is not closing the waste gate.. The two Valves side by side do the same job... SWAP them over!! Make sure all pipes are in the correct way around, but swap them over.. theres a chance your Exhaust EGR Valve could still work.

Does your Engine Diagnostic light come on?? If not, it wont as the ECU is not recording an over boost, and it wont show with Zero boost...

As for Hubs, do you mean Wheel Trims???? Pleanty on ebay on cars being broken..

Paul

[Dommo]

That would make sense Fred, should the turbo overboost (for instance due to the loose wastegate hose issue you describe), the ECU would know this and think ARGH STOP PUTTING FUEL IN BEFORE I GO BANG, and go into limp home mode.

[thorter]

There is a PSA technical description of the DW10 engine system operation at
http://www.christiantena.pwp.blueyonder ... ioperation , though I suspect quite a lot of clarity has been lost in translation.

The boost control looks like a classic computer control loop, where there is not enough bandwidth from the boost pressure sensor, through the ECU processor, all the way to the turbo waste gate actuator. Therefore, the ECU sends a faster open loop computed demand (modulated mark to space ratio) to the electrovalve. The slower overall feedback then provides a running correction to the necessary accuracy.

If then there is a discrepancy of more than a pre-programmed limit, the ECU sets limp home mode. As citroenxm says, the ECU record of this gets reset at switch on, and perhaps also if the out of tolerance does not last long.

Another thing to check is the vacuum pump connection. The clip on plastic union has a very small hole (I seem to remember 1mm) that can get blocked. Ensure this is fully clear in case there is sometimes too little vacuum, but do not drill it out to a bigger size.

Fred

[citroenxm]

There is a PSA technical description of the DW10 engine system operation at
http://www.christiantena.pwp.blueyonder ... ioperation , though I suspect quite a lot of clarity has been lost in translation.

Blimey Fred, thats a very informative bunch of info! That needs a print out and filing for reference...!

Paul

[Sulla]

Thanks for the suggestions guys, The car is in the garage on Thursday to have an engine mount replaced so I will have a chat with my mechanic about it.

Much appreciated!