Xantia V6 broken exhaust (update: and rough low rpm running)

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

xantia_v6 wrote:
Mandrake wrote:
Low compression is unlikely to cause the sort of misfire that you describe without also disrupting the idle.
I would not spend too much money (other than on a spare gasket or two) before inspecting the rear plugs, your symptoms are quite similar to those of a rear plug drowning in engine oil.
Ok I might leave the compression test for now. Do you still think it could be an oiled spark plug if the idle is perfect and the high RPM performance is only down slightly ? If it was oil, what would be causing the plug to drown in oil ?

By the way there is a small oil drip from the top rear of the engine that drips onto the exhaust and burns at high temperature - that's been there since I've had the car but I haven't done any investigation on it yet.
If your cam-cover leak is on the inner edge of the cam cover (or cam block), then over a period of months it will fill the spark plug cavities in the head.
The engine oil is contaminated with carbon, water and other stuff that makes it a bit conductive, and under conditions when the ignition voltage is highest, the current tracks through the oil rather than the spark plug.

resealing the cam covers is an interesting days work (you might as well change the timing belt at the same time).
Lets just hope it's not that then as that's not a job I'd be able to tackle with my current working conditions. (Eg an open car park, not to mention winter fast approaching...)

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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by RichardW »

Service.citroen indiates the knock sensor is on the top between the cylinder banks - however, there may well be a good bit of artistic licence there! Listed as NFP as well though...

New coil is £220 from Citroen....

There is also a temperature probe in the bottom of the air filter housing - given that yours is reading +50 or so all the time, this might not be in the best of health - mind you a new one is £30 so maybe not that urgent!

I think David Hallworth has a V6 still - might be worth a PM to see if you could borrow the coil for a test?

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CitroJim
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by CitroJim »

RichardW wrote:Service.citroen indiates the knock sensor is on the top between the cylinder banks - however, there may well be a good bit of artistic licence there!
That's exactly where it is :twisted: You need to remove the lower inlet manifold complete with injectors to get to it :roll:

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Chris570
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Chris570 »

or to test it it's a green 3 pinned plug coming out of the valley. Getting that lower manifold off isnt too bad once you're far down enough with the below job....

I'd check for oil as a priority, It's a cheap test, change the plugs while you're there and if there is oil and you remove it and all is better afterwards you're sorted. If it comes back it's the oil. It's a PITA to do the camboxes but you'll certainly need to do it if its leaking.

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CitroJim
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by CitroJim »

That's a good thought about the oil...

The inlet manifold is not hard to take off Simon.

1. Remove the coli cover on the front bank.
2. Remove the induction concertina between the airbox and throttle body. Disconnect cables and the small pipe on the throttle body.
3. Disconnect throttle cable and cruise pushrod by taking off the bracket held by three torx screws ablve the throttle body.
4. Unplug the rear bank plug leads and remove the two 10mm bolts holding the pluglead tray. One is on the side of teh rear bank and the other is on the back and below the rear bank. Move the tray and leads out of the way.
5. undo the bolts and two earth wires holding the cable tray across the engine. Disconnect the injector wiring plug at the side of the engine and disconnect the MAP sensor. Disconnect the small vacuum pipe in the vicinity of the injector connector (near engine mount)
6. Remove the studs in the lifting eyes that support the manifold at the back.
7. Remove the bar across the engine mount to the manifold.
8. Remove the 8 manifold studs, noting one is an Allen bolt.
9. Carefully lift the manifold off. It's unwieldy so get help if you can.
10. Stuff rag in the inlet ports now exposed.
11. Remove the rear 'dummy' coilpack to gain access to the plugs.
12. replacement is a reversal of disassembly. Be careful you don't dislodge the new gasket when replacing the manifold.

Replace the manifold gasket on reassembly.

Fellow V6 specialists. Have I forgotten anything?

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Post by addo »

9A and 12A are omitted from your list (they are identical). Beverage of choice.

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CitroJim
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Re:

Post by CitroJim »

addo wrote:9A and 12A are omitted from your list (they are identical). Beverage of choice.
Tea please :lol:

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xantia_v6
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by xantia_v6 »

disconnect the idle control valve connector... and when refitting the manifold, ensure that the idle control connector and the airbox temperature senso lead are sitting in the right place and not tangled under the throttle body...
be careful not to disturb any of the oil breather tubes, they are fragile and may be difficult to replace.

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Ok I just eliminated the suppressor capacitor by driving around the block with it disconnected - no change.
RichardW wrote:Service.citroen indiates the knock sensor is on the top between the cylinder banks - however, there may well be a good bit of artistic licence there! Listed as NFP as well though...
NFP means no longer for purchase ?
New coil is £220 from Citroen....
Are you talking about the coil pack ?

Eagle eyed addo has just spotted this for me on ebay:

http://www.ebay.co.uk/itm/Peugeot-Genui ... 680wt_1195" onclick="window.open(this.href);return false;

It's the correct part number, whether "genuine" means new old stock of the original OEM type as implied (in which case it would be an absolute bargin) or whether its just a pattern type (in which case its still a good deal) I'm seriously tempted. £70 is just within my "impulse buy" range, especially if it turns out to actually be OEM, while £140 and £170 are not.
There is also a temperature probe in the bottom of the air filter housing - given that yours is reading +50 or so all the time, this might not be in the best of health - mind you a new one is £30 so maybe not that urgent!
I might have inadvertently mislead everyone a bit regarding the air temperature reading - when I took that reading the engine had been run about 3 hours earlier, I assumed that would be long enough for it to cool down especially on a cold day, but apparently not. On a later morning I plugged the Lexia in to a dead cold engine that had sat over night and both air temperature sensors read 8 degrees, which was the ambient air temperature that morning. The coolant temperature sensor also read 8 degrees. From that I think the air and coolant temperature sensors are working ok, at least at the bottom end of their range.

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

CitroJim wrote:
RichardW wrote:Service.citroen indiates the knock sensor is on the top between the cylinder banks - however, there may well be a good bit of artistic licence there!
That's exactly where it is :twisted: You need to remove the lower inlet manifold complete with injectors to get to it :roll:
Ouch! #-o I take back what I said about generally good access on the V6 :lol: Hopefully its not that then.

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Chris570 wrote:or to test it it's a green 3 pinned plug coming out of the valley.
How would I test it exactly if its a piezo sensor ? Connect it to an oscilloscope while the engine is running ? Check the change in engine behaviour with it disconnected ? (Presumably running will get worse if its working or stay the same if its faulty ?)
Getting that lower manifold off isnt too bad once you're far down enough with the below job....

I'd check for oil as a priority, It's a cheap test, change the plugs while you're there and if there is oil and you remove it and all is better afterwards you're sorted. If it comes back it's the oil. It's a PITA to do the camboxes but you'll certainly need to do it if its leaking.
I certainly do intend to do the rear plugs - plugs are cheap and a gasket shouldn't be too bad. Whether it fixes the problem or not they're probably due.

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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by xantia_v6 »

A faulty knock sensor wont cause a misfire, it only causes the timing to be excessively advanced, causing pinging (or pinking I think it is called in NZ). I don't think that this is your problem.

BTW, my V6s run almost exclusively on 95 RON, only seeing 98 occasionally in France if it seems cheap.

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

CitroJim wrote:That's a good thought about the oil...

The inlet manifold is not hard to take off Simon.
Thanks Jim,

I've saved a copy of that for when I need to do it. Even if the fault turns out to be something else I may need to do the rear plugs soon anyway.

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

xantia_v6 wrote:A faulty knock sensor wont cause a misfire, it only causes the timing to be excessively advanced, causing pinging (or pinking I think it is called in NZ). I don't think that this is your problem.

BTW, my V6s run almost exclusively on 95 RON, only seeing 98 occasionally in France if it seems cheap.
Yes, it is called pinking in NZ :lol:

It's a shame you're all so far away so that someone can't drive the car and see the symptoms first hand for a second opinion, I'm struggling a bit to describe them.

Both the noise it makes (which is quite disconcerting, a kind of groaning shuddering noise) and the behaviour under load is hard to describe. There is also what sounds a bit like a noisy gearbox bearing or driveshaft exit bearing mixed up amongst the noises too, although that dry bearing sound has always been there and is similar to the noise my 2 litre auto gearbox used to make under load at low revs in 3rd as well...which I never did anything about and which never got any worse or caused any problems.

Having never driven another Xantia V6 I have no frame of reference as to how well and how smoothly it should pull between 1000-2000rpm, although it was certainly much better than this a few months ago.

One thing that bothers me too and I'm not sure if this is tied up with the fault or not, but the gearbox does tend to be very lazy at changing down a gear - as you slow down it tends to let the revs drop down as low as 1000rpm in 3rd or 2nd before shifting down, so it tends to labour the engine a lot with around town driving, its not uncommon to slow down for a corner, see the revs drop to 1000-1200, accelerate anywhere up to half throttle or even more and instead of changing down a gear it will just labour the engine at low revs until it finally picks up. If you happen to be going up a hill you can be using 2/3rd throttle and it will just sit there labouring at 1200rpm unable to pick up, if you use the kickdown it will then practically bunnyhop and zoom off like a maniac - there is no happy middle ground. I don't remember my 2 litre auto doing this, it was much more willing to change down a gear without using kick down. In these situations I've just learnt to press the sport button to temporarily change the downshift thresholds so I can get some decent pickup without using kickdown or excessive throttle.

The down shift behaviour does seem to change as well, sometimes it is more willing to change down with reducing road speed, other times it just lets the engine labour mercilessly unless you actually kick it down, use sport mode, or manually change down a gear...when the engine was pulling a bit better low down it didn't matter so much but its a major problem at the moment, I'm having to manually keep it out of the 1000-1500rpm range.

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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by DickieG »

Mandrake wrote:
xantia_v6 wrote:A faulty knock sensor wont cause a misfire, it only causes the timing to be excessively advanced, causing pinging (or pinking I think it is called in NZ).
Yes, it is called pinking in NZ :lol:
The same here, pinking :?

V6 gearboxes do tend to be rather reluctant in changing down a gear or two (possibly down to whoever wrote the economy mode program) as you say activating Sport mode livens it up nicely.