Xantia 1.8i 16v misfire

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Mosser
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Xantia 1.8i 16v misfire

Post by Mosser »

My 1997 1.8i 16v Xantia is misfiring slightly on idle and at low-mid revs (i cant tell at high revs if it is or not),
I have changed the air filter, the spark plugs and cleaned around the connectors for the low voltage feed into the HT ignition block and none of this has helped it at all,
One think i did notice was that GSF supplied me with Eyquem RFC42LZ2E spark plugs when i asked for 1.8i 16v xantia plugs, but i took out RFN58LZ, I wondered whether this had any bearing on it at all ??
Is there any way for me to find out which cylinder is misfiring without resorting to taking it to a dealer?, is there a cheap code reading tool?,
I am starting to think that maybe the HT ignition block is failing on 1 coil but as they are all joined together i cant buy 1 to check them all, but short term i was thinking of just reducing the plug gap on the offending cylinder if i can find it, I dont want to kill the cat !!
Any other ideas as to what i can do to track the problem down?
Cheers
harryb.48
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Post by harryb.48 »

Hi Mosser
Have you tried refitting your old plugs? - could be ONE dicky new plug,I`ve had this in the past.
Then if you WANT TO find out which one it was you just replace them one by one until fault occurs.
Also you could look for a plug lead shorting out somewhere along the way - best to do this in the dark.
Good luck
harryb.48
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Post by harryb.48 »

Sorry I think I misunderstood ,you had the fault Before you changed the plugs? Silly me !
Mosser
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Post by Mosser »

Yep fault was there before i changed the plugs too !!, no worries!
Plus, the 16 valver uses an integrated engine cover and HT Assembly with built in springs so i cant do anything there except change the whole module!!, doh!
Richard Gallagher
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Post by Richard Gallagher »

With a misfire like this, start with checking for inlet manifold leaks by using a length of hose and moving it all around the manifold, paying particular attention to the gasket where it attatches to the head. If a leak is present you will hear a hiss in one particular area.
This type of fault will cause the symtoms you describe due to a mixture imbalance.
Also remove the plugs and examine the colour on the electrodes, are they all the same, any difference on one particular plug will allow you to point the finger to any component exclusive to that cylinder.
Don't forget the basics of a compression test, then make sure that the throttle butterfly and its housing are clean. After that the list becomes rather long and potentially expensive, Lambda sensor, MAP sensor, coil pack etc.
This type of problem could be either fuel or ignition so if possible try to get the emissions checked as this will show up with high/low Lambda and hydrocarbons.
When it comes to cats they are pretty robust and unlikely to be damaged whilst you do this test unless you drive for some distance, and will cause a build up of fuel on the surface of the cat which then sets light to the honeycombe.
As far as code readers are concerned then the cheap Gunsons ones will only work with very early Xantias. It may well be worth paying out for a code reading as this will work out quicker and cheaper than replacing components in the hope that it will cure the fault. Bear in mind that your car does have the facility to show what is called 'datastream' i.e. Show all the 'live' information from the sensors that the ECU is receiving. The fact that the engine managment light is not illuminated doesn't mean that no faults are recorded. Whereabouts are you, if anywhere near Heathrow then I could do it for you as I have the 'magic' tool.
Mosser
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Post by Mosser »

Thanks for all that info Richard,
I forgot to mention that i have got a cracked exhaust manifold at the moment which is blowing quite badly now, i am trying to source a replacement one but havent come up with any yet,
I didnt realise that inlet manifold leaks would cause a misfire, I will go round the piping carefully tomorrow and see if it is ok,
I am going to be keeping this car for a long time now as it is really nice to drive and returns good economy so is it worth me getting a code reader if they arent too expensive?,
I am in Warminster in Wiltshire which is a fair distance from you unfortunatly, but thanks for the offer!,
I have still got my diagnostic software and lead from my Seat Leon Cupra that i used to own, it uses standard OBD2 software and the lead is a standard fitment so i am told, is it worth me plugging it in and trying it?, it is fully opto isolated and used on the K-line ?
I will get a compression tester and see if it shows anything up, i have seen those quite cheap in H*lfords for around a tenner
debutant
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Post by debutant »

Ian,
Check this out for spare parts:
http://www.andyspares.com/discussionfor ... IC_ID=8857
Cheers,
John
harryb.48
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Post by harryb.48 »

Ian,
As Richard rightly explained ,a mixture imbalance will cause the symptoms you describe.He also mentions the Lambda sensor which is situated in the (usually ) lower part of exhaust manifold.The sensor reacts to the presence (or absence) of unburned oxygen in the exhaust gases and will enrich or make leaner the mixture accordingly.
Your leaking manifold will be causing confusing sygnals from the Lambda sensor to the ECU and will probably cause misfiring and other strange symptoms eg. surging and hesitation on acceleration.However, I would normally expect your mixture to be over -compensated as the sensor detects the presence of too much oxygen due to the leak but then perhaps the intake of air fluctuates and would then cause the above symptoms.
I read somewhere that the average lifespan of the sensor is only about 50000 miles and then it can become sluggish when switching from lean to rich causing poor mixture control.
(IN optimal condition it switches back and forth ,from lean to rich in less than a second)
So my conclusion would be to fix the exhaust before trying anything else.
Regards,
Mosser
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Post by Mosser »

Thanks John and Harry,
I dont think he will be stripping it for parts yet though!!, his one sounds like yours (now mine!!) and they are far too good a car to scrap, but i'll be keeping an eye out for it
Sounds like it could be to do with the exhaust manifold then?, i might take the manifold off this morning then and see if i can seal it up temporarily with an extra gasket to get me through the MOT, and get a replacement manifold as soon as i can, i dont suppose exhaust manifolds can be welded can they? (too much heat in the exhaust gases passing through??)
JimW
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Post by JimW »

Mosser,
I'm not sure whether they can be replaced on your engine, but if so you could try new HT leads (these are probably integrated with the plug caps).
My '96 Laguna 2L 16v had a misfire (at light throttle, with a warm engine) that was caused by the insulation on the plug caps breaking down, replacement cured the problem completely.
It seems that, after asking a bit, HT lead assemblies (e.g. including caps) are one of the things that may only last a few years on more modern engines. It was suggested that on some makes you should really replace them fairly frequently - I think he was implying something like every 3 or 4 years.
If you go down this route, do try and find a set which are basically identical to the original ones. Pretty much anyone will sell you a set which "fit", but which are nothing like they really ought to be - so do check before you buy.
A suggestion for working out which cylinder is misfiring (and it could be 2, depending on how many coils there are), is to disconnect the injector wiring for each cylinder in turn - assuming, of course, that this is a Multipoint Injection system!
Yours,
Jim.
Mosser
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Post by Mosser »

Thanks for the suggestions Jim,
But there appears to be an individual coil for each cylinder and there is just a thick rubber cover covering a big spring that presses on the top of each plug to make the HT connection, they dont appear to be removeable but i will ask at my local dealers,
It is multipoint injection, but i will get my fault codes read before i do anything like that otherwise there will be loads of errors logged!!
Cheers
Richard Gallagher
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Post by Richard Gallagher »

Mosser, don't waste time and money doing anything before getting the exhaust manifold sorted, as this will be causing confusing signals to the Lambda sensor and therefore has a very good chance of being the cause of the misfire.
You car does not have HT leads as such as the coil pack plugs directly onto the spark plug.
As far as your diagnostic tool is concerned, as it is OBD compliant I take it that it has a 16 pin plug, whereas your Xantia will almost certainly have a rectangular 30 pin socket. For your info the socket is located in alongside the fusebox by the drivers right knee.
alexx
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Post by alexx »

There are 2 coils, working on the same 'wasted-spark' principle like on 8 valve engine. This HT assembly, made by Sagem, didn't prove very reliable.
Only 2.0 16V 155 HP engine had individual coils for each cylinder.
Mosser
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Post by Mosser »

Ok, thanks, time to search harder for a different manifold i think, i will trawl all the breakers yards that i know on my journeys around the country!
Cheers
Mosser
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Post by Mosser »

Just found a Xantia 2.0 16v being broken for spares on ebay, But does anyone know if it uses the same exhaust manifold?
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