specalist knowledge in 1.9TD xantias and idle speed.

[falling-out-with-my-car]

Hi,
This has probably been covered before many times in the past
But I seem unable to find a decent solution to it.
Both my Mk2 and my fathers mk1 do this.
When the engine is hot after a long run the engines want to rev up above 1000 rpm
for some reason, we have tried pulling the throttle cable back by placing our feet under the pedal
and this momentarily drops the throttle speed but it return's to 1000 rpm or slightly higher.
I have changed the vacuum valves on the bulkhead of my S2 Xantia to no effect, Ive checked the pipes and where necessary replaced the vacumn
pipes again to no improvement is there perhaps an electrical sensor that increases fuel flow/air flow when the engine gets hot by any chance?
or perhaps a timing sensor that changes the timing when the engine gets hot?
really stuck on this one Now she's a lovely car just got aged niggles.
Turning the air-con on slows the engine speed though.

Thanks

Nigel.

[CitroJim]

Have you proved the vacuum-activated fast cold fast idle system is working properly Nigel? Check that the diaphragm and cable will pull on vacuum/no vacuum and that the idle speed does in fact properly alter. Don't forget the default state is fast idle and the vacuum system must be working to obtain a slow idle when the engine is hot.

Is the vacuum pump good?

Then if all that proves out you need a Lexia/ELIT session to check the ECU is giving a correct signal to the fast idle electrovalve..

[falling-out-with-my-car]

Hello Jim,
Thanks for your reply,
yes there is a vacuum created by the pump on the end of the camshaft.
I'm guessing here but do the diaphragms fail, its a component that has been removed many times
for maintenance to the engine, I wonder if it got damaged or dropped at some point.
It seems that proving anything without access to a lexia is going to be painful.

[CitroJim]

Good, that's an excellent start Nigel, what about the results of the other tests I have suggested?

[falling-out-with-my-car]

Car is at Pleiades at the Mo having a new clutch fitted
But will test on the trip home from Cambridgeshire to Northants.
I didn't realise that the vacuum cable moved enough to detect it manually I'll put a marker pen mark on it
and make a pointer with a piece of wire epoxied to the rocker cover and align it to the mark on the vacuum cable.
and watch it to see if it moves, next time the engine plays up.
This may explain lumpy starting from cold to, even when new glow plugs & battery have been fitted?
I know the person that fitted the new head from Xac's engine used a lexia of sorts and went through the menus resetting
things to see if he could turn off the abs light even when the car doesn't have abs.

[RichardW]

What does it idle at when cold? It should be 1000 if the cold start is working, dropping to 800 when warm. When you switch the AC on it's supposed to rise back to 1000. If you are finding the idle is rising to 1000 when warm, and it drops to 800 when the AC is on, then it sounds like the system is working in reverse somehow!!

[falling-out-with-my-car]

That's exactly what it is doing Richard.
800 when cold rising to 1000 or 1100 when hot.
The air con pulls it back to 800 when hot.
sounds like its getting the wrong signal at the wrong time.

[CitroJim]

That's exactly what it is doing Richard.
800 when cold rising to 1000 or 1100 when hot.
The air con pulls it back to 800 when hot.
sounds like its getting the wrong signal at the wrong time.

That is often the case if it's ben wrongly set up to compensate for a duff cold idle system...

[falling-out-with-my-car]

so what's next step Jim a lexia I suppose the vacuum, pipes were leaking when I first got the car
but I have replaced them all now. They were split at the ends and it looked as though no-one could be bothered to check them
for damage or didn't see the splits. does anyone know what the correct settings should be please?
I know she will get a very hot engine in the Summer time if I don't crack this one before the Summer arrives.
fortunately all the fans work brilliantly.

[CitroJim]

No lexia needed yet Nigel, just watch the cable and manually pull on it to se if the idle changes when pulled a few mm either way...

A small movement of the cable and the lever it operates on the side of the pump should make a very discernible difference to the idle speed if the fast idle lever is correctly adjusted on the pump. So often they are adjusted without any understanding of how it works to 'cure' faults in the fast idle system.

You can these if the cable actuation vacuum diaphragm is good by applying direct vacuum from the vacuum pump to it and seeing if it moves..

Also, see if thee is vacuum and no vacuum between hot and cold coming from the electrovalve at the appropriate times.

A Lexia is only needed if all the above vacuum checks are good and the electrovalve seems good but does not operate.

You may have the situation where the coolant temperature sensor is duff and the ECU thinks the engine is always cold...

[RichardW]

I have a dim recollection that the fast idle valve and EGR electrovalves look the same but work the opposite hand, perhaps the wrong one is fitted?

[CitroJim]

Yes, that rings a bell too Richard...

[falling-out-with-my-car]

Are you referring to the two electro valves mounted side by side on the bulkhead just behind
and to the right of the vacuum
pump on the end of the crankshaft they do look identical? ( My Fathers VSX Mk1 doesn't have these at all but I do. on the S2).
perhaps the vacuum pipes are fitted in the wrong order?
On the other hand I do seem to recall that the vacuum pipes have a y-piece connector on them.
to supply both valves at the same time from one vacuum pipe.
The temperature gauge is reporting around 70-80 degrees C
Unless the revs rise and then she will hit 90 degrees C in the summer time.
Is there another temperature sensor not necessarily related to the engine temperature gauge then?

I almost forgot to mention this, immediately after picking the car up from Pleiades
after the new clutch was fitted I went to town and had the tracking re-done
when the car was driven out of the garage the revs were around 12 to 1300 rpm
They had been idling the engine whilst on the ramps whilst setting up the steering track rod ends
being partially indoors and not moving she got quite hot, the cooling fans were running to.
I tried the air con to no improvement so I opened the bonnet and pulled on the vacuum operated
diaphragm cable and the revs dropped to 800 and stayed there.
The cooling fans didn't stop until about 5 seconds after the revs came down again.

Nigel.

[falling-out-with-my-car]

Jim & RichardW,

Update first warm day we have had for a while Good Friday 2016.
on the way into town I got caught in traffic and the Xantia temp Gauge hit 90 Degrees C.
The idle speed rose from around 850 to 1500 rpm.
I parked up lifted the bonnet and checked the diaphragm cable which was very slack, it is taught when the engine is cold.
I pushed the pump throttle lever back and the revs dropped it is being held forward possibly by the electronic ojimmyflip
mounted to the top of the throttle lever with three wires going to it.
I think you are both on the money when you say that the system is working in reverse.
How to remedy this is a bit beyond my capabilities though.

At a guess I think there might be a motor in the plastic casing of this electrical do dah on top of the pump
and the ECU seems to be holding the pump throttle open when the engine is hot as opposed to when it is cold.
the ECU decisions seem to override the manual control of the vacuum pump, I don't really understand why the car should have both fitted
unless the pump was replaced earlier in life before I owned the car.
my Dads Mk1 has a micro switch on the top of his pump but no vacuum pump or vacuum apparatus is on his engine.
He still has similar problems with his throttle rising when it shouldn't I.e. when the engine is hot.

We have both only used two independents to work on the cars and one of them hasn't had the need to hook up a code reader as yet.
I know for sure that the other used a EBay purchased code reader on mine about three years ago when all this trouble started with my throttle.

I have had two new throttle cables fitted with new casings to the hardest bit to replace properly.
I just don't understand why the throttle is being held open when the engine is hot.

when I drove home along the A14 approximately 12 miles the engine temp dropped to 80 degrees C and the idle speed dropped back to
850 rpm.

Hope this info helps.

it would be nice to be able to have a normal journey in the Xantia without having to lift the bonnet on a sunny day.
I am dreading this coming summer as she is a lovely car to drive with working air-con and a cracking turbo boost to.
you can still feel it in your back when driving her. I've even had a new heater matrix fitted, I do hope I can get this sorted because otherwise I think she is a keeper
especially now a new clutch has been fitted as well.

cheers Nigel.

[CitroJim]

Nigel, as the cable is moving it's just a case of setting up the adjustment properly... Some unskilled person has been at it without understanding how it works...

It's not hard, just think it through and have a play at manually operating the lever the fast idle cable is attached to. It'll soon make sense.

The device on top of the pump throttle spindle is a potentiometer and not a motor... It sends a signal to the ECU so that it can determine load by way of how far the throttle is open and what speed the engine is running at...