Xantia 1.9d hesitation issues

[mirafioriman]

The last couple of days I've noticed my 1994 (L) Xantia 1.9d has been a little jerky and hesitant when driving. Had a quick look tonight and I think I may have diagnosed the problem. (The car has a Lucas pump)

Recently I replaced firstly the throttle and stop shaft seals (to cure a diesel leak) and then the waxstat and now the idle increases when cold and goes back to normal when the engine reaches 40 degrees or so.

The problem is I think related to this. The switch that controls the timing advance when cold has a split rubber allowing it to essentially flap about. Instead of the timing reverting to normal when the cable goes slack it seems to be deciding second by second whether it wants to be advanced or not

To support this diagnosis, when I set off first thing in the morning and the cable is tight raising the idle and advancing the timing whilst the engine is stone cold it runs really cleanly and pulls well. It's only when the engine starts to warm up and the cable slackens that the hesitation and jerkiness occurs.

Does anyone know if this part is still available from Citroen or anywhere else?

[CitroJim]

That sounds like a very good diagnosis I've seen those rubber bellows and contacts in a bad way before and the contacts too...

One easy way to check is to disconnect it entirely once the engine is warm and see what happens then. If I'm thinking properly, the advance solenoid is only activated when the engine is cold so as to give a tad more advance so that cold diesel has a bit longer to get burning. Too much advance when hot will not be good and will cause a lack of power.

Strictly the rubber boot is not needed. It's there to protact the contact set but if you keep everything clean and check things on a regular basis it should be ok without it...

[mirafioriman]

Is it spring loaded then? There appears to be nothing left without the rubber to prevent the contact (that's connected to the spade terminal) from just flopping around when the cable is slack.

[spider]

I seem to remember its a tiny spring with a metal button in it. I threw mine away, it made no real difference. I'd go with unplugging it as it gets its feed from the top of the stop solenoid (usually anyway two wires there) and the output goes to the advance unit.

In theory it should only operate when its stone cold and the fast idle cable is pulled fully tight.

[CitroJim]

I'd go along with Andy and disable it. Early Lucas pumps didn't have it and they relied on fast idle alone when cold with no great difficulty.

In truth the cold advance is only really useful when the brass monkeys really shiver and in the UK it very rarely gets that cold - even though it feels like it does sometimes...

If you really want to keep it then some re-engineeering of the contact set may be the way to go...

[spider]

A microswitch could probably be added to the cable end stop I'd guess although even with it unplugged you should not really have any running concerns.

As long as the fast idle cable is working that should be enough as that's something you do want as without that it will try to idle at about 500rpm when stone cold and likely cut out on deceleration for the first couple of minutes running.

As I say (although it was a Lucas pump) I ran without mine on the 205TD for seven years and never had a concern. I did have other reasons for removing though but I'll not bore you too much.

[mirafioriman]

I've ran it disconnected today and she runs ok. Will see in the morning how she runs cold without it. No joy at the dealers getting a new one!

[mirafioriman]

It was very cold today. Started her up with the advance wire disconnected. Not good, ran pretty bad for a minute or so and put out quite a bit of unburnt fuel smoke, neither of which it has ever done before. It also cut out once when part warm when I was driving (never done this before either). This could have been to do with the low idle however, I've since adjusted it as it was idling too low when warm after I had fitted the new waxstat.

We'll see what happens when I go to work in the morning

[spider]

The low idle can cause those problems.

Ensure the fast idle cable is:

1. Either slightly loose when the engine is hot (ie the cable must be free from the arm, a couple of mm is enough)

or

2. Its pulled tight when cold.

You can use either method (just glance at it later on to check the other way is correct) depending on which you prefer.

[mirafioriman]

Tried it again this morning. Despite idling at 1000 rpm when cold it did it again. Tonight with the wire reconnected it was back to normal.

[spider]

Hmm. That does sound odd as I've not seen one run 'badly' without the advance unit.

I'm assuming once its got warm its fine yes ?

An early 306 / 405 will provide parts if required from a scrapyard. Later 205TD's and 309TD's will also have this if it helps.

[spider]

I could not see the parts listed looking at 'stop and idle control' for both 205's and 405's although I know for certain some of them have them, I've seen quite a few. It just shows the usual arm and waxstat cable with its end fittings, nothing more. The advance solenoid does not appear to be listed on its own either which is strange.

[mirafioriman]

Thanks for the help so far. Yes it does run ok when warm. However, in the really cold weather we've had here recently it has stuttered a bit on starting even with the timing advance reconnected. I think I'm going to check the heater plugs in case one has gone down. It sounds like it's misfiring on one cylinder when starting from stone cold.

[CitroJim]

It sounds like it's misfiring on one cylinder when starting from stone cold.

It might be worth checking your valve clearances. It's a funny quirk of the XUD that its clearances are tightest when stone-cold and they can suffer from the clearances tightening up over time - it is very common on the 1.7 NA XUD.

It just takes a bit of heat to open them up but when stone cold one of your cylinders may have negative clearance which is holding a valve a little open and dropping compression a bit.

[mirafioriman]

Well a bit more progress

Looked at it today and discovered it does indeed come off Managed to find quite a few in my local scrapyard. Unfortunately they all had a certain degree of damage to the rubber bellows I now know that the rubber bellows are only there to protect the contacts, but also that mine was missing a spring. I've also learned that this spring is important as it is what keeps the engine fast idle off when warm. That's probably why I couldn't seem to get a consistant idle speed after fitting my new waxstat. Anyway replacement is now fitted and adjustments made. It's running fine warm and now idling consistently. I haven't started it from stone cold yet but will update you all when I do.

It also seems that the waxstat isn't just on or off. It seems to extend gradually, lowering the idle from a coolant temperature of around 40 degrees. Seems to be fully off around an indicated 60 degrees or so.