Did you use NGK IX Iridums, or NGK Laser Iridums? I'm not sure which would be best for the car and I can't seem to find the answer on the forums / internet. Thank you.

 

I very recently had a bad experience with NGK Laser Iridiums. I replaced an old set of Bosch Iridiums with the NGKs, and the engine ran and sounded really rough, and was misfiring at every stoplight. I swapped them out for a fresh set of Bosch Iridiums and its back to normal. Can't explain it.

 

To be honest I can't remember which ones I used now. However they were selected because of information I had searched for and found on this forum.

I have had no running issues with the ones I selected. I might have the ones on my purchase list for service and maintenance. I will see.

Here are the ones I purchased, NGK 7866 Spark Plug IridIFR5N10 $ 9.61 8 $ 76.88

 

Thank you very much for the info! I almost only get to browse the forums during my lunches at work so I probably missed a conversation about this somewhere, but I definitely tried to find one haha


It looks like those are the Laser Iridium in case anyone else is looking for the same information

 

I put the NGK Iridium plugs in my XJ8 as well, at around 94k miles. I didn't notice a whole lot of difference compared with the old NGKs that were in there, but I don't know how old they were. Anyway, it's lovely and smooth now

 

I'm curious if there would be any notable difference between the Laser Iridum and the IX Iridum, from what I can tell the only differences are 1. IX is a single metal 2. IX is made to last a shorter time and 3. IX cost more lol.

http://www.ngksparkplugs.com/pdf/DYK...idium%20IX.pdf

I found this article going into detail about the differences.

I'm going to buy the Laser Iridum and change my plugs tomorrow

 

The IFR5N10 are pre-gapped and have a tiny point. Do not touch it with anything. They last at least 100K miles (well, they have on my STR).

 

don't forget anti seize paste.

 

Just finished swapping out new Bosch iridium plugs with original ( in my 2005 XJR) NGK laser iridium. So I have done this twice in 2 months. Both times without having to remove the wiper cowl cover or completely take out the access panel in the brake reservoir. Simply remove all but the bottom one closest to front of car and pull panel towards front of car from top and swivel around bottom one. Makes it easier to put panel back in place as well. Reason I wanted to swap out the Bosch is that my fuel consumption went up dramatically with the Bosch compared with my original NGK iridium IFR5N10. I have not driven the car since the change back I am waiting for better weather.

 

This really helpful but pleas forgive naivety, how on Earth do I get the coils out? Most of the foul on bulkheads and the like and despite applying a certain amount of persuasive pressure it is clear they will be damaged if I apply much more. Is there some form of trick to it? XJ8 X350 2003 UK model

 

I do not know how different the 2003 model is from the 2005 so cannot help. I know I had to "manipulate" the coils quite a bit to get the correct angle for extraction on my car.

 

I'm sorry I've asked this question elsewhere but how do I get the coils out rrom a 2003 XJ8 without damaging them? They are free enough but there isn't sufficient clearance between them and various bulkheads and other obstacles and if I apply any more persausion I am sure they will break. Am I the only one who has this problem?

 

I don't remember doing anything difficult to remove the coils. I am sure it was a case of remove the bolt, move some wiring out of the way and just wiggle the coil pack out. There may have been some tweaking, twisting, pulling as you have to pull the coil off the top of the spark plug which may be where you are feeling the stuck type pressure.

 

Hi James,

Over time the coils do tend to become a little siezed in position. Once you have the retaining screw removed and electrical connector disconnected (if possible), it helps to twist the coil to help free its rubber boot from the spark plug insulator. If no amount of pulling does the trick, you can carefully use a thin, wide flat screwdriver or other tool to gently pry the casing of the coil upward, taking care to position your prying tool so it doesn't damage anything else. Prying on the screw tab may or may not work, but it may help you get enough of a gap to then get your prying tool under the coil/ignition module case so you can pry the coil more directly upward.

Once you get the coil separated from the spark plug, you can tilt it sideward to clear the bulkhead obstructions (specifically on the rear cylinders #7 and #8).

I found that with some of the coils I could not separate the electrical connector before I had pried the coil up a little. If you have the same problem, be especially careful not to damage the harness wires, which harden and become brittle with age.

It helps ease future removal if, before you reinstall the coils, you apply a small amount of dielectric grease to the inside of the boot that goes around the spark plug, taking care not to apply so much grease that it will get on the metal terminal that clips onto the spark plug. Also apply a little grease to the rubber sealing ring around the base of the ignition module housing. Unlike petroleum-based greases, silicone-based dielectric grease won't deteriorate the rubber or plastic parts of the coil. Lithium grease is another suitable option.

And while you have the coils out, you might flush the electrical connectors with zero residue electrical contact cleaner spray to help remove any oil contamination, dust or oxidation that may have developed.

Cheers,

Don

 

Rubber boot at end of coil pack

I was changing my plugs and on cylinder #8 the rubber boot, at the end of the coil, stays put over the plug. I reinserted the coil and it just won't come out; it is blocking me from grabbing the plug with socket.

Any ideas greatly appreciated.

 

thanks sir im going at today.

 

Was looking at the 04 XJ8, & discovered a much easier way to access the rear drivers spark plug, surprised that it has not been posted. The oil fill spout, under the cap where you add oil, UNSCREWS, giving your rachet plenty of room to turn. Hope this helps someone to avoid some unneeded work.

 

The manual I have at my disposal says 15Nm (11 ft/lb)!

That's a big difference!

 

If you are going to change the plugs, this should be the #1 thing on your list. Buy this magnetic spark plug socket, it's worth every penny and then some... https://amzn.to/2moXmXz

 

Or use flexible plastic tubing (like for screen washers).