TEMPERAT PROBE and POTENTIOMETER XU10J4 Xantia - UPDATE

[sbraud]

Can anyone tell me what the TEMPERAT PROBE and POTENTIOMETER units on a 2.0 16v 155bhp XU10J4 unit (1994) do




I only ask as I have an intermittent loose connection/internal break in the wire loom where these two meet and I’m trying to work out which has the problem. Symptoms are, every now and again, engine will rev up and down (almost stall to about 2000 rpm) when idling. When driving you can feel car slow slightly and then pick up. Only happens every once and awhile.

I’ve noticed if I slightly move/wiggle TEMPERAT PROBE and POTENTIOMETER wire/s engine goes back to normal.

Cheers
Steve

[Stempy]

Temp probe tells the ecu the temperature of the coolant, potentiometer tells it the throttle angle, so together with the other sensors it can work out how much fuel to inject and when to inject it. Might be worth swapping out the temp probe as they have been known to go intermittent.

[Richard Gallagher]

Symptoms are, every now and again, engine will rev up and down (almost stall to about 20,000 rpm)

With those revs I take it you have a jet engine in your Xantia then?

Steve, hope you're well,

Richard

[AndersDK]

A failing temp probe wont cause fluctuating revs ??
Intead you will have a steady rich running behaviour (disrupted sensor equals a very cold engine).

The potientiometer (also known as the throttle position potientiometer = TP) is however known to cause the engine revs ghosting around - really fluctuating - not just unstable engine revs.
This is because the TP wears out on the carbon tracks and returns insane position signals. The ECU then try to correct the "erratic engine situation" and the whole thing therefore gets very unstable.

[Stempy]

Ahhh but the probe on mine went intermittent, thus sometimes working fine and sometimes not. Giving it a wiggle would cure it temporarily.

[wheeler]

Temp probe tells the ecu the temperature of the coolant

Number 1 is the inlet air temp sensor to measure the temperature of the air entering the inlet manifold.
Number 13 measures coolant /engine temperature.

[Stempy]

You're not wrong didn't look close enough. In which case, what Anders said.

[sbraud]

Thanks Stempy, Anders and wheeler. It’s good to know what I’m dealing with.

Looking at my post it sounds as though engine is revving into oblivion. Anders explanation is a more accurate description of symptoms… more unsettled than manic.

Think I’ll change potientiometer for starters and see where we are.

Hi Richard, Jet engine might be the way to go and easier to maintain. I’m well thanks, moved house earlier this year so Xant maintenance has fallen way behind. Hope you’re well.

Steve

[sbraud]

Bad news! GSF have stopped stocking Xantia POTENTIOMETER and deleted it from stock list. I guess after 11 years parts may start drying up


After doing an internet search I found a company in Essex selling them new for £27 plus VAT with free delivery. Does anyone know one by sight or have any info on this?



My feeling is it’s probably OK as GSF only sold one for all `Injection Xantia models’ and it looks very similar to Citroen schematic. Seller too, claims it fits most early Xanita/XM models but I’ve never used them before and so want to check facts before ordering.

Can anyone recommend any other sources selling Xantia throttle potentiometers?

Cheers
Steve

[Stempy]

You could try here

http://www.autoteknik.co.uk

[rory_perrett]

FWIW had the throttle potentiometer fail on an MG Maestro a while back, gave exactly the symptoms you describe.

Rory

[sbraud]

Thanks guys...

I've sent email to autoteknik. Cheers Stempy

Steve

[BonceChops]

(disrupted sensor equals a very cold engine)

What about disconnected inlet temp sensor. Would it think it was hot or cold? When I left mine disconnected (2.1TD) the car was very sluggish especially at low revs. I am guessing it thought the inlet air was very hot so was injecting less diesel.

[AndersDK]

Hi Neil -

I have no experience with the later generation ECU managed diesels - like the 2.1TD with Lucas EPIC system. I would think though that a diesel also have an optimum inlet air temp which goes with fuel volume injected.
The inlet air temp is governed by ambient temp and intercooler efficiency - and how hot the turbo is on the inlet side.

All (most) petrol engines have an inlet air temp sensor (ATS) which works the same way as the Coolant temp sensor (CTS). I.e. its an NTC resistor element which will have its higher resistance at low temp.
Thus a disrupted ATC would behave the same as very cold inlet air.

Below a certain air temp a diesel will start missing as the fuel will not ignite properly - or not ignite at all. You need the helping heat from the glowplugs - especially at start.

I assume that an ECU controlled diesel would also have its timing modified - as this is the normal way to "choke" a diesel on coldstart.
This would certainly lead to an odd engine behaviour at idle with a hot engine.

[AndersDK]

To Steve :

The throttle potientiometer is a more or less a standard sparepart - i.e. the same part goes on several car makes & models. You should certainly not have any trouble in finding a suitable spare.
For starters its fitted to many other Citroen models like ZX, Xsara, etc. Then you have the large selection of Peugeot models which also uses the same part.