Hello,


My 2002 Vanden Plas 8 cylinder needs new spark plugs. Mechanic recommended Bosch. However, I have seen some threads that say Bosch plugs can cause problems. Can anyone advise which plugs are best?


Thank you for your response.

 

If yours is the 4.0L, then you'll need NGK Iridium IX BKR5EIX-11 with S/C or Jaguar Iridium Spark Plug - NGK 7866 in the base model. Pull one out that's in it and see, your in FL like me, its warm enough...
Personally I've never had any luck with Bosch. They didn't work in my Vette or Expedition very long before fouling began.

 

Thanks Highhorse. Appreciate your response.

 

Why would you need specific plugs?? Wouldn't any plug with that correct gap work?

How would one even know if they need new plugs without actually removing them? The factory plugs were rated for something like 100k miles...

 

get iridium plugs, find the right price: Denso was cheaper here than NGK or Bosch. Motorcraft even cheaper. I went with Denso, 26K miles ago; work fine.

 

These are performance machines, if you ever watch NASCAR and saw Jack Roush, he's always checking plugs. The correct spark for the air/fuel mixture is required to get the most out of the combustion. Too hot can overheat the head, too cold can create horrible performance and carbon build up in the head.
As for when to replace plugs, it varies per application, but electrodes wear down and lose conductivity. They start to burn yellow instead of blue (which can be a bad ignition component also) and proper spark is essential for max performance and mileage. These high energy ignitions of today require proper plugs.
If your engine stumbles, maybe rocks a little sitting at a light, you may at least need to check the plugs and maybe just regap them. Perhaps a piece of carbon welded onto the electrode or they are simply worn.

 

That's a good reason not to buy cheap plugs, but why an exact specific type? Is that a jaguar recommended plug or something?

 

Initially Jaguar sometimes has someone (usually a high end producer) make specific type plugs for them but they may be branded Jaguar. The engineers have worked out and have specific requirements to get the best performance per that engine. After a model is discontinued or the maker has an agreement for production time only to them, then that maker can start putting their name on it. In the meantime you have others who will either reverse engineer or come up with a similar kind that works almost as well to possibly even better (doubtful though). But the only way to find this out is through others trial and error. Thus why the Chinese frauds need to be watched for, they use seriously cheap low grade metals.

 

Thanks - so would there be performance loss of you installed something off the shelf high end like Bosch platinums or ac Delco rapidfires?

 

Not much, but why? Buy the the right iridium plugs. They are good for 100k miles, why go cheap? Bosch, NGK, Denso -- all good products and not that expensive.

 

Specifications Page 6-1 (Vehicle Care) lists NGK PFR5G-11E, gap 0.04 - 0.043"
(Note typo in metric gap; 1.0 - 1.1 mm is correct conversion)
NGK USA has replaced/upgraded to NGK PFR6G-13E/2341. BOTH are Laser Platinum plugs. $37.50 box of 4, on-line

 

how would i know if i got a super charge or just base? All i know is my vehicle is 2000 VP XJ8 (not sure if I should include the "L") I try to use the decoder on this site, but it did not say if it was base or S/C or/and XJ8L or XJ8. help, it is hard to order parts or find out what my car needs.

 

Spark plugs are like mass-produced beer. The manufacturers all claim that theirs are the best but it comes down to tiny or no actual variations that make a difference.

It's not worth agonizing over brands or price. Use what Jag installed and you're good for another 100K miles.

 

This should be another thread but since we're here....open your hood and if you see on top of the motor 2 rectangular boxes saying "supercharged" on either side of the motor and in between them a box that has a large cast V8 on it, then you have the R model or supercharged. Anything else is a base model motor.
Your car itself is an XJ or X308 model. You could have a XJ6 which is the inline six cylinder or the XJ8 which is the 8 cylinder. There are standard XJ's with a base body and then there's the Vanden Plas which is the longer wheel base.
Most any place you order parts from should ask you for your VIN to order the correct parts for certain things like shocks. Other than that, look on line and find an Indy (Independent Jag Mechanic) local and ask them to explain to you what you have.

 

VIN decoder here may work FordEtis home page

Generally parts can be ordered by VIN