I bought some NGK iridiums BKR5EIX-11 to replace the factory NGK IFR5N (iridium) that came out (they were .040). NGK website says .040, This forum says .051, the new plug is pregapped at .044. I am tending on gapping them the same as the ones that came out, but I am confused now. PLEASE HELP!

 

Oh well, I figured that if they came from the factory gapped at .040 and they were the NGk iridium, then I bought NGK iridium and gapped them the same. I just put them in. Whoever is advising that the plugs on the 2004 4.2 liter (non-supercharged) be gapped at .051, must be wrong.

 

Clifsmith, if you were looking at Kennedys thread about a 2001, 4.0 litre and refering to the replied post to the spark plug gap of .051 and this is incorrect then I will personally notify alldata about the "wrong" gap.

 

yes the gapping is 4.0-3.5

the iridium iv's i ordered also came in at .45, at that time i wasnt aware of the proper gap and installed as is.

i will have to re-gap all the plugs soon.

 

I saw some posts that said the initial gap spec prior to 2001 was .038 to .043, then for some reason the spec was changed to .051 for post 2001 vehicles. Now why, I have no idea. However, please note that my 2004 factory originals that I took out were gapped at .040 and that is consistent with most websites (including NGKs, autozone, napa, and other sparkplug sites.). It was interesting. On NGKs site, I went to model year 2002 for the 4.0 and it said .052. So to me it looks like the reverse. There seems to be a lot of mis information on this site and it is difficult to weed through the bad. People if you are not sure if something, please do not advise. Forums are for good information not something "you think".

So do you guys think I did the right thing to gap back to factory original .040? It is a done deal, I put it all back together last night.

 

Do you notice any difference in the operation or performance?

 

'04 model year with the 4.2 liter motor (AJ34) - gap spec should be .040
98-03 model year with 4.0 liter (AJ26, AJ27) - gap spec should be .052

 

Glad to hear that my conclusion was the right one. .040 it is.

 

Why did you buy the NGK iridiums BKR5uEIX-11 ($6.99 each price at Advance Autoparts store ) when you could've bought the OEM factory NGK IFR5N10 ($13.49 price at the same store) ? It was the price ?

 

To add the NGK IFR5N10 OEM plugs are pre-gapped to .040 Jaguar/LR spec that calls for this plug..

 

You're digging up a post that was written 7 years ago.

 

Old or not, I have been working with the Denso (4701) IK16TT in my 4.2 N/A and am well pleased. I like the performance better than both the NGK BKR5EIX-11 or IFR5N10. Gap is always around 0.038, which yields around 8~10kV to cross the gap at idle.

When it comes to gap, many don't understand the dynamics in play. The coil plays an integral part as well. In the COP design used, the maximum voltages peak is at 15~20kV, and once that is reached you can no longer provide adequate spark. (misfire) WOT creates what is called tip-in lean condition, and will always require more voltage. Seen on a scope you can watch the voltage required to jump the gap extend, as well as the burn time decrease significantly. The richer the mixture itself, also aids in the process of jumping the gap. If you come close to the limits that the coil can produce, you will not have adequate reserves, and will in fact run the risk of overheating the coil. Rich mixtures take less voltage verses lean conditions. With this COP design, you want the idle voltage from the coil to be approximately half of the total power a coil can deliver. The wider the gap, the more voltage is required to jump that gap, and the shorter the burn time will be. Modified engines with higher compression or forced induction (both criteria are present with AJ33) will typically require smaller electrode gap settings (to ensure ignitability in these denser air/fuel mixtures) as the voltage requirement at the electrode gap is increased due to higher combustion pressures. As a rule, the more power you are making, the smaller the gap.

 

My 2004 XJ8 has 123,200 miles and I got it with 52,000 miles. I think it's time to change the spark plugs, I do not know if the prior owner did. 🙄
Can some one send pictures or walk me through the process of changing the spark plugs in the XJ8 year 2004.
I have not found any videos online related to the XJ8 2004 specifically that year, my concern is mainly the driver side where the air filter box is. There is not enough room to maneuver due to the valves and houses there or whatever those connections are. I'm wondering how mechanics do it. Do they disconnect all those parts by the right side (driver side) to change the spark plugs ? Or is there a better way ? Like disconnecting the wiper cover by the winshield to get accesses to the last spark plug on that particular side (Driver side) right side if standing in front of the hood. Anyone please? Clifsmith for example, you did yours can you help me ? Or someone else.
Cheers 😎👍

 

My 2004 XJ8 has 123,200 miles and I got it with 52,000 miles. I think it's time to change the spark plugs, I do not know if the prior owner did. 🤔
Can some one send pictures or walk me through the process of changing the spark plugs in the XJ8 year 2004.
I have not found any videos online related to the XJ8 2004 specifically that year, my concern is mainly the driver side where the air filter box is. There is not enough room to maneuver due to the valves and houses there or whatever those connections are. I'm wondering how mechanics do it. Do they disconnect all those parts by the right side (driver side) to change the spark plugs ? Or is there a better way ? Like disconnecting the wiper cover by the winshield to get accesses to the last spark plug on that particular side (Driver side) right side if standing in front of the hood. Anyone please? 🤔

 

* The OE X350 4.2L NGK Iridium plugs are pre-gapped to ~0.040" (actually, 0.039"), which is correct. NGK advises against regapping these plugs

* Replacing plugs (on my 07 XJR) was straightforward. It is not necessary to remove anything (other than the head covers and coil packs, obviously).

Suggest use a locking extension on your (5/8") plug socket (to ease socket removal). A wobble head and universal (3/8 drive) are all that is needed.

My plugs (98K miles) were really dry coming out. Suggest squirting some WD 40 in plug well before removing old plug, and easing CCW and CW until the plug threads wick some lube. This will prevent head damage. Use a little WD 40 on the new plugs too (do NOT use antiseize)

Hope this helps!

 

Someone's already posted details for a 4.2 - maybe not exactly your car but it's the same (not the S-Type I think).

Take them out still fairly warm/hot! They are a PAIN to get out cold.

Do not add anything!! Not WD40, not anything. But yes, once even slightly loose work them left & right (CW, CCW).

 

Just an FYI, Jaguar service documentation does recommend anti-seize. About 4 threads worth, 3/4's of the circumference. I use Permatex 80078

 

Interesting!

Many OEM's have put out TSB's against sp plug antisieze. I used to use it myself. Wish Jag had used it at the factory, as taking out the original plugs was like undoing old plumbing.

I think it is fine if you can keep it on just 4 threads (and keep your hands clean). The stuff can apparently melt and plate the plug electrodes, causing misfire.

My recently purchased Ducati ran badly under load (though new plugs, etc, etc). When I pulled them anyhow, I found the threads (and plug bodies) gooped with NeverSeize. This bike had the coils and ECU, etc replaced by the PO hunting for the problem. New plugs and its now perfect. I'm sure that with clean hands and just 4 threads, it would have been fine. WD 40 (or equiv) is safer and easier for me

I DO use NeverSeize on all exhaust stuff, etc. Its great!

 

NGK IR5N10 plugs have an anti-seize coating. Do not add anything else.

 

I'm fully aware of the TSB from NGK, and I'm also aware that NGK plugs are what Jaguar specifies. Service documentation also specifies usage of anti-seize. You do what you wish with your vehicle, but as for me, I understand the reason for the TSB, and I understand the reasons behind using anti-seize, especially in aluminum heads. Just read above and you'll see some of the issues with installing dry, (which also includes aluminum transfer and shards of fine aluminum left) and I'll show you how easy removal is with using about 4 threads at the tip end of the plug, 3/4's of the circumference, tightened until gasket starts to crush and about 3/4 of a turn further to about 125 inch-pounds, (10.416 ft-lbs) and how easily they remove, and how there is no aluminum transfer. (secondary advantages to using a small amount of anti-seize includes thermal transfer)