Xantia V6 auto problem

[fastred]

My 2000 V6 Xantia auto has begun to show a low speed flat spot and to momentarily stall when cold.

Is there anyone with a Lexia within range of Farnham, Surrey, who could help me check the car?

Thanks, fastred

[Mandrake]

Do you mean just after starting when cold the revs will drop down to the point where it nearly stalls then recovers ? Sometimes a few times in a row before it stabilises ? Mine has started doing that again recently too, apparently its not an uncommon problem on the V6.

What speed and throttle opening are you noticing the flat spot at, and is it just a momentary hesitation/stagger followed by a rapid pull away, or is it a more just a lack of power at low revs ?

I also have a similar problem, albeit intermittent, and given the other things I've already ruled out I'm starting to suspect the MAP sensor, so I'd be interested to know what you find.

By the way, my engine ECU shows NO fault codes at all despite the issues, so don't be surprised if you don't get any fault codes on the Lexia...(still worth checking of course, as is looking at the live sensor data)

[fastred]

That sounds very much like my problem, Mandrake, a stagger followed by a return to normal running. I too thought about MAP sensor - will look at this after I get the codes checked. Thanks for the reply,
fastred

[davygr22]

Guys,
I had this issue on my 2000MY XM Exclusive with the same V6 (ES9J4) engine - it was the coolant temperature sensor on the alloy hose connection point which is located to the right of the engine block as you view from the front - it has a green plastic top for the electrical connector- Is an issue on this engine.
This sensor feeds info to the engine ECU directly & causes the symptoms mentioned when faulty....check this first as it is cheaper than the MAP sensor - if replacement doesn't cure then MAP sensor is potential culprit(Located on rear of intake manifold).

Good Luck!!

[Mandrake]

According to the live sensor data on my Lexia my coolant temperature sensor is fine, but I still get the symptoms...

[CitroJim]

According to the live sensor data on my Lexia my coolant temperature sensor is fine, but I still get the symptoms...

Simon, they can look fine but still be duff... They're cheap enough to do a change without breaking the bank...

[Mandrake]

Will replace it in due course, but it won't be until next month or maybe later. I've just received a lovely reminder that my tax disc is due on the 31st of December (couldn't have timed that better could I ) and then I have insurance due in January as well, all this on the back of a dodgy gearbox with an unknown amount of life left in it...

What's involved in the job ? I'm assuming that like nearly every other Xantia V6 job in the engine bay step one is remove the air filter box Access looks easy, but does it require draining some coolant ? Or can I just block the hole with my finger while I swap it over loosing a minimum of coolant...

[CitroJim]

What's involved in the job ? I'm assuming that like nearly every other Xantia V6 job in the engine bay step one is remove the air filter box

Yes, that's step one as always. They even recommend removing the airbox when replacing a numberplate lamp..

I'd drain down the coolant but if you don't mind a small spill then just unscrew the old one and piop tyhe new one in ASAP...

To help mitigate coolant loss, seal the expansion tank with some thin polythene sheet under the cap so that air can't get in...

[fastred]

Thanks to all for the suggestions. My local stealer wants £25+ for a new temperature sensor, but I found some information on Electronic Diagnostics which David Goddard passed to me some years ago. Here it is stated that the coolant sensor should have a resistance of 3600 ohms at 20C, falling to 350 ohms at 90C, so the first step would seem to be to check these. (These figures are given for a Renault Laguna v6 engine with Motronic MP7 control, but the sensor is likely to be the same)
The article also says: "A particularly vulnerable component to internal corrosion, due to low additive concentration in the anti-freeze, is the coolant temperature sensor. Many cars with poor running are down to this component."

I will search for a suitable bung, take out the sensor, inspect and clean it and then check its resistance. Might be a time for a coolant change as well - I last did this 4 years ago.

fastred

[Mandrake]

Let us know how you get on...