Looking for spark plugs for my X300. Handbook calls for Champion RC9YCC which I can't find but can find RC9YC at a very good price. Can anyone tell me the difference between the two. In other words what does the extra C stand for.

I would be interested in any other recommendations that you have had good luck with.

Thanks.

EZDriver

 

The C indicate a copper core to the electrode, so its not essential. Don't be tempted to use the equivalent NGK plug to a Champion RC9YCC. Generally I think NGK make excellent plugs, but for some reason they don't seem to work well in the AJ16 engine. For the same reason I can't recommend other plugs that weren't the one originally specified. You could also choose to use a harder/colder plug such as a Champion RC8YCC. I actually use RC6YCC plugs in my uprated AJ16 SC engine without experiencing plug foluing problems, but then I never drive my car round town or start it below about 5degC.

 

I use $2.64 each NGKs from Advance and they work fine in both my cars...

 

FWIW, I've used #9 and #11 Champions and NGK Iridiums. I can't feel/see/hear/measure any difference in engine behavior or performance between the three.

<shrug>

Cheers
DD

 

Thanks guys. It seems that the car is pretty tolerant on plug ranges. I have had the car for eight years. About six months after I got it I decided to change plugs even though it was running great. I looked in the book and it said RCY9CC. But when I pulled the old ones out they were RCY12CC plugs. I had forgotten that until I realized I had kept the old plugs since they were in such great shape. Since they were in good shape when I took them out I decided to buy the same plug except without the final C as it was not available. What is in the car right now are Champion RYC12C plugs. I'm tempted to disregard the book and replace with the same plug. The plugs in there now have about 50K miles on them.

Any comments??

EZDriver

 

That's a BIG difference...book calls for 9's, and you're runnning 12's? I'd definitely go with 9's...just make sure you've got the right gap on 'em too...

 

Jaguar issued a tech bulletin suggesting the 9s be replaced with 12s.

Or was it the other way 'round?

Oh, shoot! Now I've flummoxed myself. Aging is hell. :-)

Yeah, I'm pretty sure it was 9s to 12s.

Cheers
DD

 

Doug, I was trying to find that referenced bulletin. I found one that stated that the proper plug was the EBC 8143 (RC9YCC) for naturally aspirated but the supercharged engines kept the old AJ6 EBC 11480/1 plugs. Is that what you are referring to? All other research shows the 8143's for all AJ16 applications. I also remember hearing about the 12 cyl cars getting hotter plugs but cannot find that one.
I don't know. I've always used the EBC8143's in my car and never had a problem.

 

Yabbut....still beats the alternative!

 

I think that's it.

Here's what I have......which I believe is a *supplement* to an earlier bulletin (which I don't have)


05.1-07

Date
2-95

Amended 12/98

Model 1995-97 MY
Sedan (4.0l) Range

VIN 720001-812255

Spark plugs-AJ16 Engine-
Change in specificcation

ISSUE:

The spark plug specification is updated on all AJ16 (4.0L) Sedan Range vehicles to include supercharged engines.

Hotter spark plugs (part number EBC 8143) were installed on supercharged engines in production from 1997 MY.

ACTION:

Use the following spark plugs as service replacements in all AJ16 engines:

ENGINE PART NUMBER PLUG GAP TORQUE
AJ16 (4.0l) EBC 8143 0.9 mm (.035 in) 22-28 Nm (17-20 lb ft)



Cheers
DD

 

Here's this as well. It's the earlier bulletin


http://www.jagrepair.com/images/TSB/...6%20Engine.pdf

Cheers
DD

 

I'm confusing myself, I think. Not sure.

My notes show that the EBC 8143 = RC12YCC

Since the bulletin calls for *hotter* spark plugs, and in Champion-speak, higher number = hotter plug, it would make sense that the "8143" would be a #12 Champion, not the #9 Champion.


Hmmmm.

I have nothing to do right now, and a full pot of coffee. I'll do some more checking

Cheers
DD

 

Here's another bulletin. if you scroll down it says that EBC 8143 = RC12YCC

http://www.jagrepair.com/images/TSB/...rivability.pdf


Cheers
DD

 

Thanks guys. You have all been a big help. One other thing I remember just a short time after buying the car which would be about seven years ago, I met with a good Jag tech in Dallas. I asked him how often I should change spark plugs. He said every 15,000 miles which I thought was way too often. I now think the reason for that was because of the use of RC9YC plugs which was what he was used to. The ones I removed shortly after that were RC12YCC pluge and they were in great shape which was why I replaced them with the same minus the last C.

What I will do is evaluate the condition of the plugs that are in there now and make the decision then as to which plug, 9 or 12, to go with. I won't be doing this right away but will post the results as soon as I can.

Thanks again.

 

Man, I missed that one. I always thought the 8143s were 9s.

 

Interesting stuff and useful opinions. I don't really have a question, but just thinking out loud here. I've been keen to change the standard Champions on my NA 3.2 Sport, hearing so often that NGK's are superior to Champions, and that iridium's or platinum's will enhance performance in terms of starting, acceleration and fuel economy (although I haven't experienced problems with any of these things while running on the Champions) so now I'm in real doubt, especially about iridiums and platinums, I wonder if these hot plugs will end up causing engine damage. They are hugely expensive and now I suspect they may be waste of money.

I've ordered one of Andy Stodart's modified Crank Sensor Brackets which I hope will deliver the performance & economy improvements I'm looking for, so maybe I'll just get new RC12YC plugs to complement that in view of Doug's and XJRengineer's comments on the plugs.

Cheers,
Tony.

 

FWIW the only reason I went to the NGK Iridiums is that, according to a person whose opinion I value, they're supposed to be easier on the notoriously troublesome X300 coils.

Maybe so, but I started having coil problems at about 100k miles....just like everyone else :-)

I agree....save your money!

Cheers
DD

 

watch out you could run into trouble with sp's
last year i replaced the stock ngk's on my 1995 x300 with some other premium sp
had all sort of missing when the engine got hot
went back to ngk and the problem disappeared
i measured how far the electrode stuck out from the base of the thread
and i found that the ngk was about 1/16' shorter

 

After all the discussion on staying with Champion, you say NGK is stock on your 95. Did you mean they were in the car when you bought it, or it came from the factory that way?

 

my mom bought the car new and was only serviced by the dealer until i inherited and ngk's was what was in the car as installed by the dealer , probably that was in 02 or so as she did not drive much in the last years of her life and my dad used to drive her .

in my great wisdom i replaced ngk with some other super prmium platinum or iridium plugs ( forget the brand though) and for a slong as the engine was not hot , it would run ok , when it got hot ( i live in Florida) it started stumbling and missing badly