I got some great informative e-mails from some guys here in regards
to the NGK Iridium plugs BKR6EIX. I am going to be installing them
today, but I am not sure if these should be gapped at .35 or left
at .30 as they seem to come from the box. Also it appear that a
standard gapping tool is not recommended as it can snap the tip
of,and pliers should be used instead, at least according to these
guys:
In reply to a message from Mark Janzic sent Mon 2 Jan 2012:
Got them in. They came gapped at 0.30 and I left them as
they came.
My car was running pretty smooth with Champions RC12YCC’s
gapped at .38 . My problem was I have been blowing coils
left and right. Also my idle when gear is PARK has been a
little lumpy, but nothing I would complain about.
Wow. What a difference with the NGK’S. The drivability is
incredible. The idle while stopped (on D) feels like the
car is of. Idle on park has improved, but not perfect…I
have been told that when an AJ16 is lumpy only on Park,
it’s a fuel injector issue, so I am getting my injectors
cleaned or a new set.
Anyhow, I would recommend these Iridium NGK’s for the AJ16
engines, gapped as they come from the box.–
95 AJ16 4liter 6cylinder, Houston TX
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In reply to a message from andyman32 sent Mon 2 Jan 2012:
I had a set of NGK Iridium BKR7EIX for my 96’ XJR (recommended
by NGK) and the idle wasn’t smooth. I read (also here in this
forum) that the original Champions RC12YCC (or RC12YC) are
best match so a got my self a set. With the Champions
installed the engine idles smoothly,it’s amazing how big is
the difference!
A hot start, though, is a little harder with the Champion
plugs.
I’m am now a little worried as you mentioned that these plugs
blew your coils. Did you have original coils? Is it a known
problem with the Champion plugs?–
The original message included these comments:
In reply to a message from Mark Janzic sent Mon 2 Jan 2012:
If you go to the NGK website the recommended plug is the same one I
used on my car BKR6EIX. AFAIK, Jaguar recommends per their last
Technical service bulletin RC9YCC gapped at .035 for the
supercharged AJ16 XJR and RC12YCC gapped at 0.38 for N/A AJ16 X300
and XJS. I too thought I should obey what Jaguar instructed.
Just playing devils advocate…3 thousands of an inch, how much does it
actually matter when they move/wear eventually anyway? I have platinum
plugs in my old 97 Fold Explorer, and the recommended gap is .055", but the
gap when I pulled 1 plug out was only .035", ( which I suspect they all will
be) and the truck runs nearly perfectly…
If you go to the NGK website the recommended plug is the same one I
used on my car BKR6EIX. AFAIK, Jaguar recommends per their last
Technical service bulletin RC9YCC gapped at .035 for the
supercharged AJ16 XJR and RC12YCC gapped at 0.38 for N/A AJ16 X300
and XJS. I too thought I should obey what Jaguar instructed.
In reply to a message from Doug Dwyer sent Tue 3 Jan 2012:
My my.
10% Ethanol in the tank ruining pumps; wrong brand of spark plugs
and .005 inches of additional gap blowing coils; Not changing the
oil 3 times as often as the manufacturer recommends leading to
certain engine destruction; new thermostats every 30,000 miles.
Either these Jag-U Wahs are the bigest piece of cr*p ever sold to
the motoring public, OR we might be a little bit overzealous here,
I think.–
Ross - 89 XJS, 98 XJR, 99 XJR, 02 XJ8
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In reply to a message from sparkenzap sent Tue 3 Jan 2012:
Hi Ross!
we are part of an Internet forum dedicated to our cars…we
probably are overzealous.
I can’t speak for anyone else, but this isn’t normal to me:
2009/10- original coils started going. Bought 6 new
aftermarket Prenco coils. All six coils died within a year.
2010-bought 6 OEM coils. 1 failed after 4 months. Bought
new cam cover and gasket to make sure oil was not causing a
problem
2011-another new OEM coil fails.
While it’s true that I could just have gotten bad coils
from the box (what a coinsidence), I have had Champs
RC12YCCs galled at .38 all along. Are the Iridiums NGK
Bkr6ix bgoing to stop the coils from blowing?? I don’t
know, but I do know they are colder than the Champions and
that my cars performance has notably improved.–
95 AJ16 4liter 6cylinder, Houston TX
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In reply to a message from sparkenzap sent Tue 3 Jan 2012:
It really doesn’t seem right does it?..
Every one of these problems could potentially be explained
away by squirrelly 12V or ground connections, compromised
circuits or bad ECMs. Maybe these ECMs are really just super-
sensitive, unreliable Lucas garbage that have us all chasing
different phantoms all over the car?–
The original message included these comments:
10% Ethanol in the tank ruining pumps; wrong brand of spark plugs
and .005 inches of additional gap blowing coils; Not changing the
oil 3 times as often as the manufacturer recommends leading to
certain engine destruction; new thermostats every 30,000 miles.
In reply to a message from Mark Janzic sent Mon 2 Jan 2012:
Hi,
Thanks for the additional info. I’m new in this forum (and in Jag
world) and appreciate the new information given here:-)
My car is a 96’ XJR. NGK recommends different spark plugs for S/C
engines and NA engines.
The S/C engine should run with colder plugs such as NGK BKR7EIX and
Champion RC9YCC as you mentioned, and not the RC12YC (which I
currently have)
For Champion spark plugs the higher the number the hotter the plug
is. (nice charts here: Champion Auto Parts | Replacement & Aftermarket Auto Parts?
kw=Heat+Range+Interchange+%28NGK%2DDenso%2DChampion%2DBosch%
29&mfid=2)
Nevertheless with the Champion RC12YC (not CC as they are harder to
get) the engine is smoother running and idling than the colder NGK
BKR7EIX.–
The original message included these comments:
Hello, I would suggest you read this: Jag-lovers Forums - Jag-lovers
Technical service bulletin RC9YCC gapped at .035 for the
supercharged AJ16 XJR and RC12YCC gapped at 0.38 for N/A AJ16 X300
In reply to a message from Mark Janzic sent Mon 2 Jan 2012:
Hi,
Thanks for the additional info. I’m new in this forum (and in Jag
world) and appreciate the new information given here:-)
My car is a 96’ XJR. NGK recommends different spark plugs for S/C
engines and NA engines.
The S/C engine should run with colder plugs such as NGK BKR7EIX and
Champion RC9YCC as you mentioned, and not the RC12YC (which I
currently have)
For Champion spark plugs the higher the number the hotter the plug
is. (nice charts here: Champion Auto Parts | Replacement & Aftermarket Auto Parts?
kw=Heat+Range+Interchange+%28NGK%2DDenso%2DChampion%2DBosch%
29&mfid=2)
Nevertheless with the Champion RC12YC (not CC as they are harder to
get) the engine is smoother running and idling than the colder NGK
BKR7EIX.–
The original message included these comments:
Hello, I would suggest you read this: Jag-lovers Forums - Jag-lovers
Technical service bulletin RC9YCC gapped at .035 for the
supercharged AJ16 XJR and RC12YCC gapped at 0.38 for N/A AJ16 X300
In reply to a message from x300eh sent Tue 3 Jan 2012:
Hello!!
According to the NGK U.S website they are the BKR6EIXthe
supercharged…is that where you are looking??–
95 AJ16 4liter 6cylinder, Houston TX
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In reply to a message from Mark Janzic sent Mon 2 Jan 2012:
I should also add the the RC12YCC’s I removed (which where only in
there for about 3K miles)where pretty black. I would not go as far
as calling them carbon fouled but they where more than a little
gray.–
95 AJ16 4liter 6cylinder, Houston TX
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In reply to a message from Mark Janzic sent Tue 3 Jan 2012:
Hi,
I’m looking in the UK NGK site
(http://www.ngkpartfinder.co.uk/car_commercial_search.php?
type=SPARK%2520PLUGS&manufact=JAGUAR&model=XJR%2520%252888–
%253E97%2529&engine=4.0)
I guess it’s something with US car spec and Europe car spec
that may be different.
My car didn’t like the BKR7EIX, though now I’m a little
concerned that the RC12YC I have may be too hot and cause
damage, I will consider moving the the colder RC9YCC. BTW, I
found out that prior to the BKR7EIX I had Champions RC10YC4
from the previous car owner.
This plugs issue really leaves me wondering which is the
right plug and gap for my car or any other Europe market
XJR6…–
The original message included these comments:
According to the NGK U.S website they are the BKR6EIXthe
supercharged…is that where you are looking??
In reply to a message from x300eh sent Wed 4 Jan 2012:
Mark:
I agree that your coil situation is different from what you would
expect. But, my MY 95 has not failed a coil in the 100,000 miles
under my ownership (230,000 + on the clock) and I guarantee that my
plugs are signficantly higher gap than 30 thou, since they were 38
when I put them in when I first got the car.
BTW, I am not advocating letting plugs go 100,000 miles, but on
this car, I do not fix anything that isn’t broke, EXCEPT fluids.
It idles great, I bet it will run with any six and it handles
pretty good.
And, I don’t doubt that there is some correlation between coil high
voltage failure and spark gap, BUT it is extremely hard to believe
it is so sensitive or that that your failure rate is caused by the
8 thou additional.
When I put new plugs in, I will probably leave them where they
came, as long as they are consistent and between 30 and 38.–
Ross - 89 XJS, 98 XJR, 99 XJR, 02 XJ8
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In reply to a message from x300eh sent Wed 4 Jan 2012:
So, what do we think the difference is between plug recommendations
for US and ROW? It is unlikely weather, since we have about the
same span. That leaves highway maximum speed, driving patterns,
fuel, and potentially warranty issues. Or am I missing something?–
Ross - 89 XJS, 98 XJR, 99 XJR, 02 XJ8
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