I will take the plugs out this weekend and eyeball the brand.
Thanks for confirming a few things.
That 2002 Moto Guzzi LeMans must be an impressive ride..

 

I pulled the front plug this morning and the are champs. I will replace them this weekend.
Can anyone share what the gap should be on the plugs?
Thank You.

 

That plug looks almost brand new to me. Not the source of the misfire.

 

The brown stain is normal?
Where do you buy your coils?
Cheers.

 

The brown stuff is called a corona discharge stain (nothing to do with the beer)

PLUG STUDIO / NGK

 

Post 16 in this thread has all the plug specs.

Gap: 0.9 mm (0.035 in)

.

 

so, again, swap the coils when you put it back together.

 

Go to post #30 here:
https://www.jaguarforums.com/forum/x...s-93966/page2/

You want a coil that has that specific Made in Japan sticker (probably in place on the other side of the coil you pictured)...indicating it came from Diamond Manufacturing. SNG Barrat and a couple other vendors mentioned in the thread will have them...but be very specific when you place the order.

Cheers
DD

 

It's a rare day that I disagree with you, Mikey but today I must....but only because we're talking X300s here ! Were it any other car, I'd remain silent.

I battled a mystery misfire with my X300/XJR for a couple months. I'll spare everyone the agonizing details. This miserable episode is how my XJR became known as "The Tormenter" .

The fix was replacing spark plugs that were only a few months old and were visually pristine. I went over the Burma Road and back again, chasing my tail, with the assumption that the plugs simply looked too good to be the problem.

Boy, was I wrong !



Cheers
DD

 

I'll defer to your far greater experience. Do you see something in the pics that makes you suspect it, or is it based on your own example?

I recall getting a bad plug straight out of the box too. Must be almost 45 years ago and was on a Norton 750 Commando. Looked perfect in your hand, ran great till it got up to highway temps.

 

No, that plugs look fine. On any other car I'd use and not think twice

X300s have plug sensitivities, it seems. Many report problems just switching brands (although I never experienced that, specifically) and others like me report misfires caused by seemingly perfectly good plugs.

I have no good explanation.

There might be some sort of fiddle factor involved.

Cheers
DD

 

Unless you are sporting "Precision German Engineering" from Bavaria, then it is apparently indicative of serious compression leakage, or some such!
https://www.jaguarforums.com/forum/x...9/#post1457185

Doug, if it solved your problem, then the plugs it was. I am curious if your misfire was a constant, every-day, all-the-time thing? Or intermittent?

From my own experience with this fabulous strain of motorcar.....the Holy Grail of Champion sparks is just a bunch of hooey. As I pointed out in my massive cam-cover thread, I fit NGK Iridiums at 85k and recently replaced them with the coveted Champions at 195k+ or so. I didn't take particular note of what was resident prior to the NGK's. Did it have a misfire? Yes and no. Did the change to NGK's affect it? Not in the least - but the misfire was not why I changed the plugs; I had owned the car from 63k to 85k and figured it was time. Did the switch back to the coveted Champion Coppers affect it? Not in the least. "Wait. Zane, what do you mean, "Yes and no?" It either misfires or it doesn't!"
Over the years, I've been able to narrow it down and identify some triggers:
My misfire is entirely confined to an occasional coughing, sputtering, rough start-up and anywhere from 10-30 seconds of rough running. This happens probably 50% of the (rare) times that I park it in the house-garage. (we have a 1-car attached garage(nominally wife-parking) and a 40' X 40' shop out back where I normally park.) Doesn't seem to matter if it's an hour or less or I manage an overnight in the house-garage, I'll get the rough start/misfire about half the time, probably worse in summer than winter. But wait! There's more. If I park it up for a week or more out back in the shop, I can expect the same thing, often as not. This is exceedingly rare as it is my daily driver and very rarely ever sees more than a 3-day weekend off. However, not so rare as being parked up that long at the airport, when I have to do some business travel - but have never had a rough-start/misfire episode there. I can, however, count on the radio head unit to be unresponsive to any of its buttons and remain that way for 2-5 days of operation when I board it to come home from the airport. Lastly, about 1 in 4 or maybe 1 in 5 of the times I stop by Motorcarman's shop, it will do a similar thing, starts fine, lights right off, but sits there missing and loping in front of him. Again, it smooths out quickly...and these aren't visits where he has wrenched on it. I don't recall it ever doing it when I've started it inside his shop, after a code-read or something, nay, it has ALWAYS been when I fire up to leave having parked out on the drive, stopping by to pick up parts for S-type's or drop something off, or just solve some of the world's problems with him.
Since recently fitting the Champions, I've parked in the house-garage once and had a bad-start then. I just recently returned from some travel with the family where my X300 spent a week and a day parked in it's normal berth in the shop out back, and had perhaps the worst episode of it I can remember. A false-start, followed by a coughing sputtering start followed by 30 sec of rough idle. That was last night, just moving it out to get one of the kids' trucks in to keep the air-hockey table dry...I let it come to operating temp before shutting it down. Fired'er up for a quick run to town today and it was perfect. I parked it out in the drive behind the $200 X300...which has a bit of a full-time misfire. Yes, EXACTLY the same full-time misfire it had before I fit the famed Champions as part of its recent cam-cover refurb. I suspect the coil on #5 as it is non-OEM and was also the one that was full of oil from the corroded spark-plug bore in the cam-cover. Near as I could make out through the corona (both the stains on the plugs and the ones I'd been consuming prior to trying to read the p/n's on them, I removed NGK Platinums from the $200 car. I've thus far seen absolutely no difference whatsoever in how either car runs with or without the Champion plugs....then again, I had a Champion plug fail in my 1979 Jeep CJ when it had 7800 miles or so on it (BOTH! the Jeep and the plug!!!) and haven't trusted the Champion brand since. So I do admit to a bit of a bias against Champion...though I've ordered a third set recently for fitment to the lad's 96....cause sooner or later I know I'll have a misfire issue with at least one of the X300's and I may come here for help and I don't want the wrath of the assembled forum to descend on me for not having the proscribed CHampion plugs......

So obviously, my take is that my '95 misfires because she is a moody B that prefers the relatively open-air of the metal building over the stuffy, hot house garage but doesn't like to sit out there un-noticed for days on end while I am obviously off handling other motorcars. She understands the business-travel issues and "knows" about rental cars but figures they are "professional" and I will never give my heart to one. However, to keep me in my place, she occasionally flirts with Bob and all but invites him to run his hands up under her bonnet....

 

Every day, but only after 15-20 minutes of driving

Cheers
DD

 

Thanks - sorry I missed the info on the plug gap.
I will go ahead and change the plugs and order a few coils and take it from there.
I will keep you all posted.
Cheers.