Xantia idle problems

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irisgrunn
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Xantia idle problems

Post by irisgrunn »

I slowly start to regret buying this car.

Now that I've sorted out the suspension, the car is having problems with idling. From what I can hear the car is idling and running fine. But when I rev the car and release the gaspedal the rpms drop way below the idling speed. Usually it picks up speed but sometimes the car stalls completely. IMHO it's not really hunting idle because it only drops once and then it picks up again.

I tried:
- Cleaning the idle control valve
- Replacing the idle control valve
- Inspected all hoses for leaks
- Used brake cleaner to find leaks
- Took off the entire throttle body to clean it too (I removed lots of oily gunk)

Cleaning the throttle body seemed to help a little bit but tonight the car stalled again. At this point I don't know what to do to remedy this problem. Also I'm wondering if it's at all possible to connect this car to a computer to read the codes.
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xantia_v6
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Re: Xantia idle problems

Post by xantia_v6 »

It should be possible to read the codes, but you need to use a Lexia code reader (or the earlier Elite code reader), There are few generic ode readers that understand the early Citroen ECUs.

Which specific engine variant does your car have?

Does your stalling happen both with the engine cold or hot?

I would suggest checking the the adjustment of the throttle position sensor on the throttle body, as the ECU needs to detect when the engine should be idling.
irisgrunn
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Re: Xantia idle problems

Post by irisgrunn »

The stalling only happens when the engine is warm. The TPS is basically just a potentiometer right? That would mean I could measure it with a multimeter.

The car is from 1993, 2 liter and has 8 valves, so it's a XU10 RFX (according to Wikipedia).
irisgrunn
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Re: Xantia idle problems

Post by irisgrunn »

So a couple of days ago I replaced the throttle position sensor. The car has definitely improved, when I release the gaspedal it's not shocking anymore. But it still hasn't completely resolved the idle issue. I guess the leaves the MAP sensor but I can't find it, does anyone know where it's located?
peter306
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Re: Xantia idle problems

Post by peter306 »

It's hiding behind the inlet manifold, if I remember rightly on my uk spec car I had to take the air filter box of to get accesshttps://frenchcarforum.co.uk/forum/download/file.php?mode=view&id=42049
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i5xp
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Re: Xantia idle problems

Post by i5xp »

I might add that the MAP sensor is mounted to the left side of the firewall with an bracket and has a vacuum hose running to it, at least on my 1996 2.0i 8v RFX Xantia. On the 16v cars it is under the manifold I believe.

I had an very similar issue that was solved eventually after replacing the idle control valve (first time I got an dud which complicated things). I also replaced the MAP sensor, fuel pressure regulator and spark plugs. Still idles a little low when in Drive but never enough to stall. I think replacing the throttle position sensor might cure my issue, since it's original and (likely) very worn.
peter306
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Re: Xantia idle problems

Post by peter306 »

i5xp is right, that photo is for the later 16 valve models.
According to Haynes it's on the underside of a mounting bracket, left side looking from the front, about level with the strut top.
irisgrunn
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Re: Xantia idle problems

Post by irisgrunn »



Seems to be getting worse, it's doing this as soon as the engine at tempurature. Any ideas? (except for scrapping the car).
Last edited by myglaren on 21 Apr 2022, 21:01, edited 1 time in total.
Reason: Video Link
i5xp
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Re: Xantia idle problems

Post by i5xp »

Are you sure the idle control valve is working right? Since you say the valve is new, make sure it is exactly the same shape as the old one. I got a slightly different one from a parts store, event though their computer said it's the right one and that one didn't idle at all.
Mine was hunting for idle exactly like that when the valve was broken. I don't recommend playing with the valve because mine stopped working at all after moving the head in and out for cleaning, seems like there is a position it must to be in and it doesn't self calibrate.

Fuel and ignition is probably good, as it seems to run good from what I can hear on the video.

A lexia scan tool with the 30pin harness might give some very useful insight, but pretty hard to come by nowadays.

Also, disconnect the battery for a night and charge it up if you haven't already done so. The ECU is not the smartest on this engine and seems to go crazy, especially when playing around with sensors and stuff, so it needs a reset sometimes. I would start from this.
Rhothgar
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Re: Xantia idle problems

Post by Rhothgar »

I've no advice for you as it's a petrol car but that idling is incredibly consistent in its range.

You definitely need to read the fault codes with a Lexia if you can access one.
irisgrunn
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Re: Xantia idle problems

Post by irisgrunn »

So I removed the battery for about an hour and now the idling seems to be perfectly fine. I really don't understand what's going on anymore. Just hope this time it stays like this.

irisgrunn
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Re: Xantia idle problems

Post by irisgrunn »

So I found someone with a Lexia and the right cable :-D

Unfortunately we found nothing conclusive. According to the Lexia there's nothing wrong with the car. We did some tests and everything came back good. We though that it looked like idle control valve was kicking in too late. All tests were fine though. So this afternoon I measured the resistance between the wires on the idle control valve and the ECU and they're al less then 1 ohm, so perfectly fine. The vacuum hose going to the MAP seemed cruddy so I replaced it with a brand new one.

Still no difference :cry:

I recorded a tiny bit of the testing on the Lexia and to me it seems like the MAP is reacting really slow. Does anyone know how quick it's supposed to react?

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xantia_v6
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Re: Xantia idle problems

Post by xantia_v6 »

20 years ago when I owned a Xantia with the 2l 8V engine, I found that disconnecting the battery every few months was necessary to stop the engine stalling when cold.
Rhothgar
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Re: Xantia idle problems

Post by Rhothgar »

irisgrunn wrote:
23 Apr 2022, 21:38
So I found someone with a Lexia and the right cable :-D

Unfortunately we found nothing conclusive. According to the Lexia there's nothing wrong with the car. We did some tests and everything came back good. We though that it looked like idle control valve was kicking in too late. All tests were fine though. So this afternoon I measured the resistance between the wires on the idle control valve and the ECU and they're al less then 1 ohm, so perfectly fine. The vacuum hose going to the MAP seemed cruddy so I replaced it with a brand new one.

Still no difference :cry:

I recorded a tiny bit of the testing on the Lexia and to me it seems like the MAP is reacting really slow. Does anyone know how quick it's supposed to react?


Be careful measuring resistance with no load ie continuity. You can get continuity from just one strand of copper whilst all the others have corrosion around it and get a low reading providing you hit that clean core. It is always better to test a wire with a small bulb in series as that will load the wire and give a more accurate idea of whether the wire is fine.
irisgrunn
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Re: Xantia idle problems

Post by irisgrunn »

It's just too erratic. Yesterday it was fine, today it idles between 1200 and 1800 rpm, it shocks at lows speeds and when I release the gas.

According to the Lexia, the fuel part and related sensors are fine. Now I'm wondering if the crankshaft sensor might be acting up. Could explain everything and they're only a tenner. So I'll just order a new one.