If you plan on performing maintenance and repair yourself, it is a good idea to obtain the JTIS manual as each operation is described in detail.

 

I'm curious about your negative experiences with NGK spark plugs. I've always found Denso and NGK plugs to be of superior quality and longevity. Please elaborate....

 

Ditto.

But I *really* like Denso.

Denso has a new platinum design out. The TT series has a pin like working surface on the ground electrode to alleviate quench. Waiting on a set from rockauto at the bargain price of $1.84'ish each.

With Denso in the plug wells, everything in the chain will be Denso from the ECM to the plugs.

Bosch plugs are like their oil filter brethren ... shiny and pretty on the surface ... but not really special and far too many "almost fits" due to trying to cover too many applicatons with too few part numbers.

 

While I can appreciate the curiosity concerning my experiences with NGK spark plugs, it is out of the scope of this thread to get into a debate concerning what spark plugs one chooses to install.

What I can tell you is that on more than one occasion I have experienced failures of the alumina insulator on NGK's spark plugs. For that reason, I will not use them on any vehicle I own or work on. Curiously, that has never occurred with Bosch or Motorcraft.

Other than seeing them on a Toyota, I have no personal experience with Nippondenso's (Denso's) spark plugs.

 

I have no curiosity at all about your preferences. I was agreeing with Jon89 on his preference for Denso and NGK plugs. And describing a newly introduced design.

Almost all spark plugs have alumina insulators. The usual cause of cracking/shattering is impact from a plug socket. That applies to any brand.

As for scope, there was no mention of brand until your anti NGK statement in post #20.

 

The alumina insulation failure of the NGK spark plugs occurred inside the cylinder with no evidence of impact of any kind. That is why I will not use them.

 

Well!

 

That's...really...not good. Can't say that I've ever dealt with, or even heard of, that particular issue myself. Then again, I'm a little paranoid & YMMV.

 

one case of a spark plug failure does not make the whole company bad.

im with the guys on good results from NGK and Denso plugs,i have used them in many supercharged cars and TURBO cars,(Mazda RX7 BIG turbo rotary engine).

just two weeks back changed plugs in my V12 Jag, from standard Motorcraft plugs to NGK Irridium, i have used many plugs in the last 60yrs, the NGKs IR made more power ,more torque, easier starting, and smoother idle, than anything i have ever used.

and yes i used antisez on the threads, been using that for 40yrs.

 

Good grief---you must be even older than I am!However I must agree with you completely---I had Mazda RX7s for 20 years,including single turbos and twin turbos.NGK and Denso were the only plugs I used.My preference was NGK because they were less expensive.Yes I also used anti-seize.
Whoever wrote the NGK Bulletin should have been required to remove a seized plug from an RX7 BEFORE he wrote it!

 

Or pay for new heads on a Ford aluminum head engine out of his own pocket at full dealership pricing

 

Quite right. Especially when it doesn't seem to be recorded elsewhere. Just did a search.

The condition of the engine is completely unknown. It is possible that the incorrect heat range was used, the engine suffered from detonation or the plug was dropped on its nose before installation, or suffered other abnormal abuse.

The heat range notation system on the NGK/Denso brands is the reverse of that used by American brands such as Champion and AC Delco. It is not inconceivable that someone unfamiliar with that fact could be installing hotter plugs when they thought they were installing colder plugs.

On the other hand, complaints of electrodes going missing in service on aftermarket Bosch plugs are all over the place.

 

As for the Bosch - that could also be because someone adjusted the electrodes improperly. I am sure that if you ask the people that are talking about it are only quoting what they read on the internet and I would bet they are French models as well.

 

I can only speak from practical experience with the NGK spark plugs. The correct heat range was chosen and installed and the electrodes were correctly adjusted. The spark plugs were not dropped on their 'nose' nor did they suffer any other abuse prior to being installed; they simply failed.

If one does not have any practical experience to draw on other than performing a 'search', they should refrain from speculation and drawing faulty conclusions.

No further comment is needed.

 

They are accounts on boards of roughly the same stature as JF itself, and accounts on JF.

"electrode adjustment" is unlikely as the accounts are about the super duper multi-electrode variants like the +4. Those are usually installed as-is.

Now, here's the kicker ... how about self electrode adjustment due to incorrect application specification by Bosch.

I have had the exact application specific Bosch part next to the Jaguar specified NGK. Not the +4, but the conventional design. The Bosch was noticeably longer than the NGK when measured from the gasket surface to the furthest surface of the ground electrode. The surface that would be closest to the piston head. That puts the electrode closer to the piston head using the Bosch recommended plug than the Jaguar recommended NGK plug. It's simple geometry. I checked it because something did not look right and the check was done before I ever heard about dropping electrodes.

Now, what if the longer reach works on most Jaguar V8's, but on the odd tolerance outlier of both plug and engine, there is contact? Electrode breakage is certainly a possibility. And that's on the conventional design. The +4 may be worse.

In my experience, Bosch pushes the envelope in cutting down the catalog numbers used in specifying applications. That results in non-exact substitutions. Cheaper for them, frustrating for the consumer.

 

Comment is indeed required.

You presume a lack of practical experience with NGK plugs. You further presume that a 'search' was done as speculation.

Both are incorrect presumptions on your part.

The 'search' was done as a matter of fairness, to widen the commentary beyond personal experience. For those that would like to repeat the search the terms used were NGK, sparkplug, insulator combined with breakage and fracture.

So far, you have only recounted your negative personal experience with NGK plugs and have extrapolated that into a condemnation of NGK plugs. You further somehow deem that as sufficient to discount the collective positive personal experiences of others with NGK plugs.

Furthermore, despite your obvious strong dislike for NGK plugs you have not chosen to say how many times you have seen the exact failure that you claim as justification for your opinion and whether it is completely unique to NGK. Nor have you offered any independent evidence, anecdotal or otherwise.

You might as well say that you once tripped over your shoe laces at Dunkin' Donuts, so everyone else must stay away from the brand.

BTW, you cannot guarantee that a plug has not been dropped unless you have had personal custody of the plug in question from the assembly line to the vehicle. You can assert that you did not drop the plug while it was in your possesion, but not that it had never been dropped in it's lifetime. Nor can you guarantee that you didn't happen to get a bad plug.

 

Consider the population at Jaguar Forums at the time of this post:

Threads: 70,256
Posts: 650,182
Members: 71,160
Active Members: 4,844

That information is publicly visible at the bottom of the home page.

Consider further that NGK has been the Jaguar specified spark plug for some years both as factory fitment and as dealer replacement. This means that most owners will be using or have used NGK plugs in their Jaguars.

It would be reasonable to postulate that within a large population, if a problem was prevalent it would be mentioned often enough to be noticeable.

So, how does one gather the data?

One way is to search all threads using the built-in search facility with a search term that is designed to be as inclusive as possible while still addressing the target.

So, use these two searches: NGK insulator or NGK nose

The result in each case is 5 threads for each search. 1 of the 5 must be discounted as it is this thread. That leaves 4 threads as candidates in each of the searches.

A reading of the threads will show that while the threads contain the search terms, they do not mention anything about the nose breaking.

Contrast this with the famous tensioners near and dear to the hearts of Jaguar V8 owners: upper tensioner

500 results. There are actually more because the forum software caps the results at 500.

It would be completely reasonable given zero mentions of inherent defects to conclude that there is no known problem with NGK plugs if one considers the posts on Jaguar Forums to be the equivalent to posts from NGK users given that NGK is the standard Jaguar fitment. Any claim to the contrary is just not credible.

Bear in mind that the population of JF is far bigger than the population sample used for big dollar paid surveys done by organisations considered to be "statistically significant", and that unlike a formal survey, there are no canned questions. A user is not limited to posting about a predetermined topic.

 

I am not denying that NGK is the recommended plug what I am saying and I have always said that installing Bosch plugs or any other plug in your Jaguar is not the end of the world. As you know we have down this road before and I will continue to defend any plug that is stated to be Junk. As for the posts about Bosch failing in my 5 years on this forum and 6,900 posts and a few years as moderator I did not see any posts from anyone that had a direct failure with Bosch plugs but maybe one. Using the right plug for the correct application is critical and should not be taken lightly. You will at times have a plug that might fall short of providing you what you want and that is true with most everything. I have been installing Bosch +2 & +4 on all of my Jaguars for many years and I have yet had a problem. In fact they are presently in my xk8 & s-type today.

Plums I respect you and what you bring to this forum and I would in no way want to take that away from you. You are entitled to your opinion however we (you & I) do not agree on this one.

 

All spark plug manufacturers suffer from the occasional defective plug reaching the marketplace. Perhaps it is only one in a million, but it happens. When it happens, I understand the negative opinion formed by the individual it happened to. But it has never happened to me in at least 35 years of changing my own spark plugs....

As I said, I've had great experiences with all of the Denso and NGK plugs I've ever used. I've also had great experiences with the simple, inexpensive Champion plugs that are recommended by Dodge for my 1999 Ram. The build sticker under the hood even specifies that only Champion RC12LC4 plugs should be used in this 5.9 litre V8 engine. So I've stayed with that plug throughout my ownership of this truck. No spark plug issues have ever occured, I can find them on sale for no more than $1.25 each whenever I need a fresh set, so I have zero complaints even though Champion has not been considered to be a world-class spark plug manufacturer in decades....

 

Just had a coil pack failure today on the highway on the way to work, with my wife driving. With no Jag dealer in Salem, and me needing to be to work, I had her take it to the Ford dealer. $223 later, they'd replaced the coil ($80) and the associated spark plug ($8) for a lot of labor cost. Had it not been essentially an emergency (50 miles from home), we would have limped home and either done it myself or gotten my Porsche-mechanic roommate to do it for me for a fraction of the price.

Am I whining about "poor me" to a bunch of people that may or may not have sympathy for me? Sure. Will it do any good? No.

Called the Jag dealer to check on their price for a coil: $136. Found a pack of six on eBay for $200. I want to pre-emptively replace the remaining coils soon, as well as the plugs. From reading this thread, it sounds like a few gaskets are in order as well. Anything else I should consider? Note that I've had this car about a week, and it's my first Jag.

Thanks for listening.

JD