I have a 1995 XJ6 that I bought new. The original coils lasted ten years. I replaced all six with Jag coils from Welsh Enterprises. Those lasted ten years as well. Since then the coils seem to last between one and two years. I've tried various ones.

One suggestion I had on Jag Forums was to leave the coil cover off which I did for a year or so. It was awfully ugly. Then I had the idea to just leave the gasket off the coil cover for ventilation which I did. I hasn't been long enough yet to tell if there is any benefit. I also thought about putting a spacer of some sort between the cover and where it mounts using longer fasteners but haven't done so.

I throw this idea out there for what it's worth if anything.

Comments?

bliving7

 

Bring the gap out on the plugs to 40 /1000 of an inch to reduce the current / heat degradation on the coils and use Kapton tape on the barrel only part of the coil

 

Buy only coils manufactured in Japan by Diamond.

SNG Barrett sells them.

They are the OEM manufacturer. If you do a search you’ll find other discussions about this.

 

Item # 4 / option # 2 / 103.60 each

https://www.sngbarratt.com/us/#!/Eng....2/4.0%20LITRE

If the coils have already degraded closing the spark plug gap down to the original 0.035 inch may help for a while as a better spark as there already on the way out . 0.040 is for new coils to get them to last longer .

Jaguar TSB :

http://www.jagrepair.com/images/TSB/...cing%20MAF.pdf

 

How about using heat shrink tubing around the coil body as additional insulation and to keep the body of the coil from touching the side of the well?

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Hi bliving7 I have done exactly what youve suggested, I used three small fibre washers about 2mm thick, one under each fixing point, and no gasket, of course I've no way of telling if it's of any actual benefit, other than finding a way of taking temperature readings under the coil cover before and after. But like you I figured it would help, I've seen no I'll effects of this either.

 

My experience with aftermarket coils is that they are suitable for about one year.
When I bought the car 2 years ago, it had all coils original, 6 months later one coil failed, replaced with aftermarket from britishparts.co.uk. After another 6 moths others started fail.

Original old ones where at that half working state, some cracked but still worked. Whats interesting that misfires and other stuff happened mostly in winter time. In cold climate car was almost non driveable. In summer though coils did their job better. Cold and humidity for sure had a very negative aspect to them.

So decided to replace them all at once with cheap ones from ebay. Set of 6 coils round 80 Euro. Noticed that they hold one year. This year also bought another set and changed them all again without looking which is maybe still good.

I think 80 Euro per year is not so bad, compared to headache off constantly failing ignition , misfires and no joy while driving. Also compared to OEM coil prices this alternative is much cheaper.

 

I still have my original coils on my 95 6cyl . I've owned the car since 2001. I am another that didn't replace that cover. I fell it just holds a lot of heat.

 

No need to cover the coils in any way, simply put some dielectric grease on them, job done.

When I bought my current x300, 3 years ago(~120k miles), out of 6 coils, 5 were cracked and cam cover badly burnt. I've fixed them by remelting the plastic and they worked fine for about a year and then 4 failed within a month. Replaced all with cheapo ones(from the old car where they worked for 2 years) and just had the third one fail a week ago, previous one failed last summer. Still have two spare ones from the old car, after which I'll try Lucas branded ones.
Original ones at over $110 a coil are way overpriced for what they are.

 

Are these coils unique to only this car, X300 6cyl ? Is this Ignition Technology?????, I replaced ONE coil in over 50 years of driving and that was on a 74 Gravely 12HP tractor. Never had a coil go bad on a car. Maybe I'm just lucky in that respect

 

I believe this particular coil is unique to the X300 and also the late model XJS. I think a big part of the problem with these coils is their location inside the cam cover, the heat and vibration of the engine directly below them has to be a contributing factor for the short lifespan of some of these coils.

Most of the older cars with a distributor and a single coil usually had the coil mounted in an area where it was cooled by the surrounding air flow. Coils already run hot just by the way they work, burying them in top of the engine, I never thought was a particularly good idea. Most engines today probably use the c.o.p. design. I don't know how other car brands and models hold up with this design.

Heat is the enemy of any electronic component so maybe leaving the coil cover off or even modifying the cover with slots or holes for ventilation might be a good idea?

 

Yep, COP and "coil packs" seem to have more issues, but perhaps they are higher voltage/stress than old coils? Not sure.

I've had to replace coils on more modern cars with COP or "packs" and never had to on my old distributor based cars.

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In my experience, no advantage to the present-day Lucas branded units. They're just brand-X with a Lucas stamp and Lucas box...but no better than other brand-X.

Of course the original coil were made by Diamond Manufacturing with a Lucas label as well....but at least they lasted!

IMO, A) seek out (and pay for) the true Diamond coils or B) pick whatever brand-X is cheapest. Intermediate choices don't seem to have any advantage.

I wonder what Jaguar is selling these days?

Cheers
DD