xantia 2.0 activa pinking

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stephen burch
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xantia 2.0 activa pinking

Post by stephen burch »

I have a 1997 xantia activa 2.0 8v turbo that has done 149000 miles. The engine seems to be in a reasonably healthy state and goes very well, but I do have an annoying "pinking" problem. I have tried DX injector cleaner in the tank and driven hard but it still persists. As these cars are totally computer controlled and I cannot adjust anything, does anyone have any ideas. I have yet to take the plugs out for evaluation but it does not misfire although I have noticed a slightly offbeat exhaust note when idling as if the timing were out. There is also a slight oily smell through the air vents as the car warms up bit this disappears fairly quickly and does not return throughout the journey. Any help would be much appreciated as the local garage with the necessary equipment charges £40 plus vat just for diagnosis. Thanks.
RichardW
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Post by RichardW »

Pinking is caused by the timing being out usually, and this should, I think, be controlled by a knock sensor on these engines. It is possible to test the knock sensor somehow with a multimeter and hammer (really!), but I can't remember the exact details.
Diagnostic test might not show up anything, as if the sensor is producing some kind of signal, then the ECU won't show a fault code, even if your ear tells you it's not the RIGHT signal!
Don't know how expensive the sensors are, but it might be worth a punt changing it out to see what happens, or at least examining the wiring to it. Can't help you with where it is though....
Richard
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Post by RichardH »

As far as I understand it there is a knock sensor in the cylinder head which works a bit like a microphone. The engine management computer is self learning and adjusts the timing continuously, effectively "listening" for the point where the engine pinks and then retards the timing a bit. This is why fuels like Shell Optimax are supposed to give extra performance, the engine management system adjusts to the higher octane rating. I suspect that you'll have to bite the bullet and get it analysed.
Richard
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Post by adrianeaton »

Hi Stephen
I only have experience of a BX 16V, however I'd say your knock sensor is probably sending some sort of signal as RichardW says. When mine started to play up the ECU warning light would come on and the car would hesitate and not pick up as well as it would go on to a 'safe' map.
If the car is otherwise running correctly it might be worth changing the plugs and leads/dizzy cap/rotor (if it has any!) or changing the brand of fuel you use. It can be useful to disconnect the battery for a while once all the old fuel is out of the system as this will reset the ECU.
By the way, the knock sensor on my car is mounted near the oil filter on the front of the engine and looks like a round doughnut with a bolt down the middle holding it to the block, and a 2-pin ECU plug. Be worth cleaning up the wiring at least.
Has any major work been done on the car like a cam belt change that might be the cause of the problem?
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Post by surfer »

Hi,
Knock sensors are usually peizometric in function, which is why hitting them will change their electrical output.
Pinking can also be caused by:
Old/and or incorrect spec spark plugs, especially ones where the temperature rating is way off, or maybe by carbon build up on a valve, causing a hot spot which ignites the air/fuel mix before the spark plug does.
Another possibility is that boost pressure is excessive, especially under full load.
I don't know how the wastegate works on an Activa, but I believe that it is usually electro-mechanical , with the ECU providing the control.
As most other people have already said though, it's probably timing,
although if the ECU does not provide the correct mixture under load, the engine runs too lean and again, pinking occurs.
Regards,
Simon.
alexx
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Post by alexx »

On my BX I noticed pinking under load. It was certanly caused by carbon buildup, as after head gasked was changed and head/valves decarbonised, it's gone.
Of course, there's no ECU and knock sensor on the engine...
stephen burch
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Post by stephen burch »

Thanks all for the info. I contacted a citroen specialist today and he seems to think that it's the timing. He has the necessary equipment to do a diagnostic check and if it is just that he can back it off a couple of degrees. I reckon my heater matrix is leaking as well as I have a wet carpet on the nearside footwell and as it hasn't rained recently and the car hasn't been washed for a week it is unlikely to be the screen seal leaking. The water level seems to have dropped in the header tank as well. I'll get him to check the heater connections as this comes on when it feels like it and seeing as the dash has to come out to do the matrix then this can be done at the same time. I would tackle the matrix myself but if anything else goes wrong then the car is off the road longer than expected. Not an ideal situation.
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Post by wheeler »

water could have been gathering there for much longer than a week.under the xantia carpet its like a large sponge and it can take a while to soak.if the scuttle panel is needing sealed then the water comes in through the heater blower motor intake which could also be your heater problem.taste the water on the carpet by rubbing your finger on the dampness then onto your tounge to see if you can taste coolant.
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