SOLVED Xantia s2 2l 16v missing... and missing

[pseud]

Hello Folks

I've replaced the coil pack at some considerable expense for a new Valeo unit; also replaced about Xmas were the sparks.

Symptoms (before replacing coil pack)
1. in high gear low revs engine misses to the point of dying - very embarrassing, plant foot at lights with a long queue behind and the car dies...
2. if I drive it like a sports car rather than a saloon keeping revs over 2k and preferable around 3k, then runs OK
3. it's intermittent, it usually catches itself and bursts into life before dying completely - typically I start to pull over to the left with a queue of cars behind, an irritated driver starts to pass and is then startled by the Xantia roaring into life and charging off (at which point they stop being irritated and start becoming angry...)
4. turning the engine off seems to temporary cure (reset?) the problem - if I'm having trouble and concerned I need some predictability I can cure things by turning ignition off and on
5. it pops in the exhaust - especially on over run - nothing very loud or alarming, just a gentle pop burble pop... (So, I'm guessing this is ignition and not fuel?)

All the above and with 70k (miles) on the clock I was led to believe it was simply time for a new coil pack...

And after coil pack change
1. it seemed fixed - yah! I could start from a high gear and it would pull like a train, but...
2. it seems to have degenerated - or, was it just wishful thinking and I was deceiving myself? Anyway, it does seem better since the coil pack change, but it's still occurring

So, there it is. I am hoping that some good soul has some suggestions. I've looked over this thread:
http://www.frenchcarforum.co.uk/forum/v ... g+ignition" onclick="window.open(this.href);return false;
Which from my search seemed closest to my symptoms. However, my problem is definitely low revs high torque. When power's delivered from high revs and low torque the problem seems to largely disappear and I can drive pretty happily (except from pulling away from the lights in anything but boy racer style). I spend a lot of time driving in 3rd.

Have a good weekend
Morgan

[Stewart(oily)]

I have seen a failing coil pack take the ECU with it, that was in a 307, the car still ran but was just not right

[Zelandeth]

Not got any specific experience with petrol Xantias I'm afraid, but based on experiences with other marques, the next thing I would probably take a look at would be the crankshaft position sensor as it sounds like the timing is going awry.

[addo]

It could even be the battery terminals.

[pseud]

Thanks guys.
Hmm, not sure I'm ready to blame the ECU just at the moment...
Bat terminals rock solid, but I will be looking at the tdc sensor and will report back.

[Mandrake]

Unlikely to be the ECU.

Can you get it on a Lexia ?

[Timmo]

having had similar when my coil was going in the BX, i would be first tempted to put in new plugs, i used to go through plugs quite frequently, but changed the coil and solved it,
if its been running on the plugs and missing then be worth swapping them out for new and checking, IMO.

[xantia_v6]

Unlikely to be the ECU.

Can you get it on a Lexia ?

It could be a partial failure of the transistors in the ECU that drive the coil(s).

[wurlycorner]

Is the ignition circuit on a Xantia 16v similar to that on a Xantia CT 8v?
If so, take a look on my Activa profile thread (link in signature vvvv ) and you'll see what I have found.

[pseud]

Yup, solved it - the Lambda sensor. Smooooth

Thanks

[CitroJim]

Excellent