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

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

Post by CitroJim »

Stempy wrote:Many moons ago in the days of CRT televisions we had a spray that you squirted on the anode cap to stop them arcing over in damp houses or those with heavy smokers. Probably on the COSHH banned list now though...
Gosh, that brings back memories...

Tellys that had been in heavy smoker's homes were revolting in the extreme :evil:
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Post by addo »

It pickled everything!
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Stempy wrote:Many moons ago in the days of CRT televisions we had a spray that you squirted on the anode cap to stop them arcing over in damp houses or those with heavy smokers. Probably on the COSHH banned list now though...
Dad used to use a smear of a particular lithium grease under TV anode caps after cleaning up the surfaces - seemed to do the trick nicely and last a long time as the grease is a good insulator and made the rubber cup air tight, as lack of air tightness was the real problem compounded by ingress of dust and/or smokers stain... :roll:

Of course a TV anode cap doesn't sit at 100+ degrees like the top of an engine so I don't think lithium grease would stand up too well long term if applied in the spark plug / plug lead boots etc...(it would tend to melt and run away...?)

Last time I fitted the plugs/leads on the car I used a smear of "proper" recommended high temperature silicon based "dielectric" grease in the plug/lead boots, when I had the plug leads off to swap the coil pack over I noticed that the smear of grease has turned into small dry rubbery congealed lumps of silicon. :evil:

Not impressed by that, I won't be using silicon grease on plug boots again...at least lithium grease would just go a bit runny when hot, not turn into little hard lumps! (Although would lithium mineral grease attack the boot rubbers ?)

Does anyone apply anything inside spark plug / lead boots or do you all just leave them dry ?
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Post by addo »

I use the lightest smear of Nulon L90 usually. The tech support guys told me it's a mineral based grease (and therefore not ideal for rubber), but the quantity applied wouldn't be likely to damage the boots.

My take on greasing the boots is to help them slip on more easily - I have no requirement of the grease to keep moisture out - that's the job of healthy rubber boots themselves. If I found a tangible residue of grease upon removal, would consider that I'd put too much on.

Can you get "Explorer" socks in the UK? I find they go well with my boots.
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Would spark plug boots not be made of a mineral oil/grease resistant material like nitrile though, since they're in a harsh environment that would be subject to oil leaks ?

I have no idea what the outer layer of the spark plug wires is made from though - its not very tough and is relatively easy to damage through chafing on sharp edges, (like, say, the sharp teeth in the plastic wire guides) as I've found out the hard way... :roll:
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Post by addo »

It's "Bougiderm" :P

I'd be seriously looking at options perhaps trialled by warmed over 406C pilots, of remote mount triple coils.
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Too much sugar tonight ? :twisted:
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CitroJim
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Post by CitroJim »

addo wrote: I'd be seriously looking at options perhaps trialled by warmed over 406C pilots, of remote mount triple coils.
The boot might be a good place for them...
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Mandrake wrote:
Stempy wrote:If it's running well then for petes sake leave it alone!!!!
Can't though - I know its not permanently fixed at the moment because I only changed the coil pack and I know the coil pack I took out is almost certainly ok and that the one I've now put back in was was one that was previously misfiring badly before I last took it out last spring.

My conclusion (also based on other evidence) being that rather than being unlucky enough to have 3 faulty coil packs including one that was new, that the swap has simply disturbed the fault.

If I just leave it alone and don't identify the real problem conclusively then as sure as the sun rises and sets it will start playing up again, it's just a matter of time whether days or weeks,
Make that days... ;)

Sure enough, the misfiring started to come back a bit over the weekend with the new coil pack still in place and nothing at all touched, not even the bonnet opened. It wasn't terrible but the effortless performance of the previous few days wasn't there any more. So on Sunday I took the top cover off the engine and did this:

Image

Image

Might be a bit hard to see in the pictures but I removed the protective conduits, added a layer of 3M self amalgamating tape (which has a very high voltage rating and can effect an air tight seal) at the suspect spots, and refitted the conduit, and also left the top cover off so that there is nothing pressing down on the wires.

Here's the thing though - I couldn't visually see anything wrong with the insulation of the leads, and I looked pretty closely all the way from where they come out of the top plastic guide on the manifold to their ends. A slight bit of abrasion in places due to having them in and out of the guides so many times but no puncture wounds or chunks missing.

Before I added the tape I also tried a snap throttle test while poking and prodding the leads in various ways - pushing them towards the chassis or pulling them away, and I couldn't really notice any difference - the stumble/hesitation while snapping from idle was always there, which was a little disappointing as I was hoping the symptoms would change as I moved the leads around.

Despite not finding anything wrong, after refitting the leads the stumble while snapping from idle was mostly (although not completely) gone, with driving performance immediately and very obviously better...(the engine was already warmed up and was driven 10 minutes before and after the modification, the battery wasn't disconnected etc)

So I'm still none the wiser as to the precise nature and location of the fault except that its definitely ignition, definitely something under the top plastic cover, but its not the coil pack as that was not removed.

An internal break in one of the plug leads that changes as the lead flexes or is pushed around ? (They're carbon resistance leads, although oddly the Citroen documentation claims they're solid wire leads used with resistive plugs)

A problem with the connection between the lead and the coil pack ? (can't see anything wrong with them)

A problem with the primary side connection to the coil ? (I did wiggle the plug slightly while trying to affect the throttle snap symptom, with no change) I've measured the resistance from ECU connector to coil pack connector on more than one occasion and never found any problems, nor is there any visible problem with the tension of the contacts on the plug and there is no corrosion.

Very puzzled.... the intermittent problem is right there in front of me under that top cover somewhere but I can't see it or find it... :roll:
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by CitroJim »

Simon, I forget now but have you replaced the leads?

If you have and you still have the old ones then make up a set of leads using solid wire.

I'm almost completely certain those leads should not be resistance ones and should be solid.
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

CitroJim wrote:Simon, I forget now but have you replaced the leads?
Yes I have, twice... :(

The first pair I fitted around September last year - shortly after the new coil pack - after that it still didn't run properly. A month or so later I discovered a small tear like a flap of skin in the black outer sheath of one of the wires due to the teeth in one of the guides nicking it - I taped it up and suddenly it ran perfectly for two weeks.

Happy that I'd found the problem I then bought a second set of leads around November, took extra care to fit them carefully (although no matter how careful you are, getting them into the guides above the inlet manifold at the correct length so the cables reach at both ends is tricky) and it never ran properly like it did with the previous leads with the damage taped up...

Of course at the time you assume it must be something else - new leads, extra care fitting them, surely they can't be faulty, right ? So I moved on to investigate other things, and ruled out the possibility that the leads might in fact be causing trouble again.

But I've now come full circle - definitely an ignition misfire and an electrical fault of some sort, but its not the ignition primary drivers, (proved by the symptoms returning despite the substitute ECU still being fitted) it can't be the coil pack unless I'm really unlucky to have the original faulty, second hand replacement faulty, and new replacement all faulty!

It's not spark plugs - this time it has the correct types in and when I removed the previous set (which were also the correct types) their condition was impeccable with clean white insulators, unlike the dirty fouled ones that came out the time before that. (which were the wrong types - my mistake)

That leaves the spark plug leads as the only other ignition component, so although I've already replaced them I have to face the possibility that either they're faulty from new (very unlucky for me if so) or that despite my extra care they've been damaged again, somehow.

The inlet manifold has been off so many times in the last year that its possible that they've been damaged or further damaged because as you know the wire routing and lack of spare length is such that a lot of strain is put on the leads every time you remove and fit the manifold...yet I haven't been able to see anything wrong with the leads, at least not the parts I can get to.

One thing that's very odd about the first replacements that got the hole in them is that I later cut the lead open and found there are two layers - a black sheath and an inner white insulator which looks a bit like Teflon or polyethylene foam - most of the insulation thickness is the white Teflon like substance, yet in the faulty lead the white insulation did NOT look damaged in any way! Only the outer black sheath had a small tear in it.

Yet I know for a fact that the insulation was flashing through at this point because (a) taping it up fixed the symptoms for 2 weeks, and (b) when it started misbehaving again after two weeks the spark had clearly burnt/melted a hole right through the tape at this exact spot, which is only possible if it was flashing through the inner insulation...

So it seems to me that the insulation is not of particularly high quality if its relying entirely on the outer sheath and the inner insulation flashes through so easily... :?
If you have and you still have the old ones then make up a set of leads using solid wire.

I'm almost completely certain those leads should not be resistance ones and should be solid.
I sense Deja Vu Jim :lol: We've had this exact conversation before a few dozen pages back... :mrgreen:

The Citroen service notes from Sedre/Docbackup definitely agree with you that the spark plug leads are NOT resistance types, this is probably where you got the idea from, however both my original leads that came out (which did have two intermittent breaks) and both sets of replacements that I bought, seemingly genuine Bougicord - are resistance leads of approximately 6k ohm, and all have measured as such.

I even managed to find specs online for the part number which agreed they are resistance leads, so despite the Citroen documentation to the contrary, they seem to be resistance leads.

Why they fit both resistance plugs and resistance leads I don't know - given its a waste spark system that's about 18k of total series resistance from two spark plugs and the leads all in series, which seems like a lot.

I don't have any complete leads left unfortunately, the originals I threw away, and the first replacements which had the tear in the sheath I cut the ends off to make up adaptors for my neon spark testers:

Image

I do still have the cassette from that set but it only has stub leads about a foot long on it now.

I'm not sure how I would go about making a solid wire replacement - as far as I can see the leads that go down into the cassette are moulded in and can't be removed ?

By the way to correct a mistake I made in an earlier post - the plug leads are NOT carbon resistance leads, they're wire wound resistance leads with a very fine spiral wire wound on a small former which is then encased within the "Teflon" layer, then within the outer sheath.
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by falling-out-with-my-car »

On "cats Direct" online the cat for a 2.9L xantia starts at £67 I dont know what size engine you have
but I reckon you could get a cheaper cat from them and do the job yourself.
we found them a bit pricey on postage but essential when we bneeded a self fit exaust occasionally.
checkout the law statements and if your car was registered before the date that appklies to each exhaust componant it could save you a packet.
regards Nigel.
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

falling-out-with-my-car wrote:On "cats Direct" online the cat for a 2.9L xantia starts at £67 I dont know what size engine you have
but I reckon you could get a cheaper cat from them and do the job yourself.
we found them a bit pricey on postage but essential when we bneeded a self fit exaust occasionally.
checkout the law statements and if your car was registered before the date that appklies to each exhaust componant it could save you a packet.
regards Nigel.
I'm assuming that you're responding to a much older post in this thread as otherwise your reply has come somewhat out of left field... :lol:

Yes its the 3L V6 however I'm very dubious of a £67 cat for the this engine after all the dissuasion I've had from CitroJim and others about the poor quality of after market cats for this engine, and the difficulty they have passing an MOT.

I'm not sure yet whether the cat is dead or not, at the time I got the MOT test with the high readings there was a rather bad ignition misfire which would have sent the HC and CO readings through the roof and have been working the cat very hard trying to clean it up.

I'm still trying to get the ignition misfire completely nailed first before worrying about a cat as fitting another cat with an ongoing misfire could ruin the new cat. Come spring if I've solved the misfire issues and the engine is running well I'll take it for an emissions test outside of the normal MOT - if it passes with flying colours I'm in the clear, if it fails or struggles to pass that will give me a few months warning to sort something out.

I'm more inclined to try to source a known good original factory cat from a breaker and get it welded in place rather than go for a cheapy pattern part.
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Post by addo »

I would never buy a used one. Seriously not worth the welding. The originals, I was once told, were Australian made. How's that for a supply chain?

My pick of the aftermarket is currently Magna-Flow, who make quite nice weld-in ceramic cats with all-stainless casings in the original large size. About £80 (posted) plus VAT off US Fleabay.
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Re:

Post by Mandrake »

addo wrote:I would never buy a used one. Seriously not worth the welding. The originals, I was once told, were Australian made. How's that for a supply chain?

My pick of the aftermarket is currently Magna-Flow, who make quite nice weld-in ceramic cats with all-stainless casings in the original large size. About £80 (posted) plus VAT off US Fleabay.
So £80 for just the cat section with a couple of stubs to weld onto ? Not too bad I guess, although the tail end of my cat is already missing its outer sleeve and is relying on a U-bolt style clamp to hold it together, so it might need a tail fabricating as well.

So you reckon a Magna-Flow welded in place is going to perform and last a lot better than the generic "complete fit" pattern exhaust/cat systems that places like Kwik-Fit will try to sell you on ? I think some of these exhaust chains wouldn't know what a welding torch was if it came up and welded their behind... :twisted: