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 »

Did the oil just fill the square plug wells or did it actually go down into the spark plug tubes ? In theory the rubber boots should seal at the top of the tubes and keep oil away from the plugs even if the square wells were full...

Re the capacitor - yes that's the exact one I have my eye on, although I was looking at it from a supplier other than Farnell. There doesn't seem to be much else in the same sort of size and shape. No voltage or temperature ratings listed for that one that I can see though...
Stempy
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Stempy »

The oil filled the entire plug tunnels right up to the top and took ages to get out. The plugs and insulators were completely submerged. It was a horrible job cleaning it all up.

The cap at Farnell is specifically for automotive use so should tolerate being strapped to an engine.
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CitroJim
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by CitroJim »

Oil is an insulator - hence why transformers are filled with it. It only becomes a problem when it gets full of dirt - which it will in a plug well - and then it becomes conductive an causes mischief...
Stempy wrote: The cap at Farnell is specifically for automotive use so should tolerate being strapped to an engine.
Good find Stempy :-D

Your avatar is well spooky :twisted:
Stempy
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Stempy »

CitroJim wrote:Oil is an insulator - hence why transformers are filled with it. It only becomes a problem when it gets full of dirt - which it will in a plug well - and then it becomes conductive an causes mischief...
Stempy wrote: The cap at Farnell is specifically for automotive use so should tolerate being strapped to an engine.
Good find Stempy :-D

Your avatar is well spooky :twisted:
I have an account with CPC/Farnell and buy most of my electronic supplies from them.

The avatar is courtesy of Iron Maiden :rock:
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Hell Razor5543
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Hell Razor5543 »

I would replace that cap as a matter of course. It is probably acting as a "noise" suppressor. The engine bay of any normal car is very "noisy" electrically. There is a spec page for the caps;

http://cpc.farnell.com/jsp/level5/modul ... 529929.xml" onclick="window.open(this.href);return false;

A couple of things I have heard/remembered. When we used to have analogue TVs, did you ever see interference when a vehicle with a scruffy sounding engine (usually a scooter) went past? I certainly did. I also remember a story on BBC1 Watchdog, about a problem with Ford and their cruise control, which was not properly shielded. What could happen was it (sort of) engaged, and pulled the throttle wide open. Hitting the brakes didn't dis-engage the cruise control, as it had not properly engaged to start with (what would have worked was to properly engage cruise and then tap the brakes). One driver was forced to knock the car into neutral, coast to the side of the road, and turn off the engine. Another driver hit a tree. A mechanic was able (on camera) to re-produce this problem, merely by popping off an HT lead and letting it arc to the chassis. IIRC a couple of suggestions were for the cruise ECU to be properly shielded, and to make sure the suppressor was correctly fitted.
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CitroJim
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by CitroJim »

Don't worry James, the cruise ECU lives in an aluminium box strapped to the B pillar. No fear of the same happening...

All Citroen ECUs are very well shielded but yes, no harm in replacing that capacitor...

I know how electrically noisy a V6 engine bay is.. Remember I blew up an automatic gearbox ECU :evil:

back in 1976 us apprentices spent a week at the BBC World Service Transmitting station at Crowborough learning about proper wireless. Ones you built with TIG welders...

Anyway, one of our number had designed and built his own electronic ignition for his Avenger. It worked really well right up to the time we passed the perimeter fence whereupon it promptly packed up. It really didn't like several hundred kilowatts of RF up it...

It was there learned the meaning of 'Rusty Bolt Effect'; the mechanism by which you could listen to the BBC World Service on the fence on a damp day...

I also there developed my love of big diesel engines. The station had a Napier Deltic standby power generator... We were allowed to observe it at very close quarters whilst it was run up... Did that engine sing! This was the same engine as powered the Class55 Deltic Express Locomotives on the East Coast mainline...

Happy days and happy memories..
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Hell Razor5543
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Hell Razor5543 »

Hi Jim.

I wasn't concerned about the cruise control, as I had seen one of yours and the casing looked decent. The reason I mentioned it was to illustrate how "noisy" an engine bay gets, and that even equipment designed to go in the engine bay could be adversely affected by unplanned for RF "noise".
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Since today is sunny and there is nearly 2 weeks of bad weather due starting tomorrow I thought I'd try to get an ignition suppression capacitor locally so I could try fitting it...

Try being the operative word. :roll: The first auto electrical place I visited and asked if they had any ignition suppression capacitors I got a "what's that then Pal ?" honestly the guy had no idea what a capacitor was. :lol: No luck at the other couple I tried either so rather than waste a sunny day in frustration I'll just order the one Stempy linked to online and wait for the weather to fit it... :twisted:
CitroJim wrote: Recall that I dealt with a car suffering almost exactly as the Ausiefrogs one did and that was fairly and squarely the coil. Have you got your name against the one on Will's scrapper Simon?
What specifically do you think goes wrong with the coil packs to cause these symptoms ?

They don't seem to fail outright, so do you think its due to an insulation breakdown on the secondary winding limiting the maximum available spark voltage ?

Eg when the cylinder pressures are low and the spark gap only needs about 3-5kV to fire it works, but when the cylinder pressures are high under wide throttle and the spark gap requirements increase to 30kV or more the spark just jumps internally inside the coil pack, or jumps through a crack in the outside of the coil pack to the chassis ?

If a flashover is occurring through an exterior gap I wonder if its possible to seal the external cracks with some epoxy glue to prevent leakage/flashover to the engine chassis ? (Assuming epoxy glue had high enough dielectric strength and heat resistance) Even the new coil pack that I fitted last year had a number of cracks in the outer housing after just 6-8 months of service.

On the other hand if the flashover is internal - from secondary to primary for example that wouldn't help...
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CitroJim
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by CitroJim »

Ignition suppressor capacitors went out with distributors and points Simon. I'd challenge anyone under fifty to know them intimately or where to put them so cut the old boy some slack as I guess he was a mere callow youth trying to earn a pittance as a Saturday boy so he can wine, dine and **** his girlfriend tonight...

I don't know exactly what fails in a coil but I'd be happy to go along with an insulation breakdown when it's hot. I had one fail like that on my first V6. Fine for a short while when cold and then one whole coil died turning the V6 into a very rough V4 :-D It puts the EML on...

I suspect the cracks are the root of the problem. In themselves they're not a problem but will allow the ingress of muck and air which will set up tracking paths and oxidisation..

The one that failed on the car in question had already suffered an attempt to repair it with bath sealant!!!
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Post by addo »

You could probably run LS1 coils without any changes to the ECU.

With the cap, I don't think it is for anything except the wireless. Try chopping the wire and driving around for a bit until the normal fault returns.
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Post by CitroJim »

addo wrote: With the cap, I don't think it is for anything except the wireless.
And only for long and medium wave wireless at that.
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Post by addo »

I'd never considered that aspect! =D>

Anyway, Simon didn't buy a suppression cap from the factors, so counter boy gets no pay, which means he gets no cuddles tonight. :lol:
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Post by CitroJim »

addo wrote: Anyway, Simon didn't buy a suppression cap from the factors, so counter boy gets no pay, which means he gets no cuddles tonight. :lol:
Poor lad :cry: Simon, see what you've done now :twisted: :lol:
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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:Ignition suppressor capacitors went out with distributors and points Simon. I'd challenge anyone under fifty to know them intimately or where to put them so cut the old boy some slack as I guess he was a mere callow youth trying to earn a pittance as a Saturday boy so he can wine, dine and **** his girlfriend tonight...
He looked well into his 40's Jim, so not a callow youth I'm afraid :lol:

Besides I'm 37 and my first two cars ( '77 and '84) were Kettering systems, possibly the third one as well. (can't remember what it used off hand but being an '88 it may still have been Kettering)

A points capacitor and a filter capacitor (which is what this is) are two very different things though, many Kettering systems won't work at all without a points capacitor (weak, easily blown out spark due to lack of the coil/cap ringing on discharge) whereas a filter cap isn't nearly as critical. It certainly won't stop the ignition working but it may cause increased levels of noise to enter other electrical systems.
I don't know exactly what fails in a coil but I'd be happy to go along with an insulation breakdown when it's hot. I had one fail like that on my first V6. Fine for a short while when cold and then one whole coil died turning the V6 into a very rough V4 :-D It puts the EML on...
I'm surprised yours put the EML on! I've never been able to get the EML light to come on on mine with any ignition faults, in fact not even a fault code on the Lexia. Even if I disconnect one plug lead it will happily misfire without fault codes logged, and I was under the impression the MP7.0 on the ES9J4 doesn't even have misfire detection.

I was thinking about the possibility of misfires on this engine being less "obvious" than they are on most cars due to the wasted spark system. On a normal one coil per cylinder system you'd typically have only a single coil faulty at a time which would cause a single cylinder misfire. A single cylinder misfire is REALLY obvious because of the uneven beat it causes which makes the engine vibrate and rock in an obvious way.

On the other hand in a wasted spark system if a single coil fails then in many cases (depending on the nature of the coil failure and whether it affects both outputs) TWO cylinders will misfire, but they will always be cylinders that are exactly opposite in the firing order so the uneven beat of a single cylinder misfire will not be present, although "roughness" and "raspiness" increases, and obviously power will be two cylinders down, which is a lot.

Furthermore the injectors are wired in parallel in 3 pairs of 2 as well, so a fault with one of the injection signals from the ECU (such as a poor contact at the ECU connector) would cause two injectors to fail in opposite phases of the firing order, again causing two cylinders of lost power and increased roughness, but not an uneven single cylinder misfire. (I've checked the injector waveforms only a week ago though and all look ok and are identical)

This possibility of an opposing pair of cylinders misfiring together does tend to fit in with what I notice - large intermittent power loss, increased roughness and engine noise, but not an obvious misfire like vibration. (the engine sounds more raspy when revving under load when performance is poor, but is smooth and a lot quieter when performance is good)

So an intermittent misfire on a pair of cylinders could indeed be the major cause of power loss.
I suspect the cracks are the root of the problem. In themselves they're not a problem but will allow the ingress of muck and
air which will set up tracking paths and oxidisation..

The one that failed on the car in question had already suffered an attempt to repair it with bath sealant!!!
:lol:

While the outer black plastic housing is cracked, I wonder whether the epoxy moulding that the coil is in is cracked as well. A crack only in the outer housing may not necessarily cause an issue unless it exposes a crack in the inner epoxy resin of the coil as well...
Northern_Mike

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

Post by Northern_Mike »

CitroJim wrote:Ignition suppressor capacitors went out with distributors and points Simon. I'd challenge anyone under fifty to know them intimately or where to put them



How very dare you! I am a mere 40,and I can both remember how to set up points, capacitors and set timing on an old fashioned engine.

I can also, having worked on modern engines for so long, suggest where you might like to put such devices nowadays.