First question this is exciting.

So after finding a box of spark plugs in the boot I decided to have a look at the ones in the car. The first 2 where a bit oily the seconds 2 where a tad orange in colour and the last two where more of a grey then a orange.


What plugs should I be using sadly as the car is still stuck 45mins away from my house and I have to visit her I cant give any numbers although it would appear the ones currently in the car are different to the ones in the boot.

I know its a very simple question, I also know 0 about anything relating to cars.

are you referring to the first two as the front two plugs nearest the radiator ?
When referring to cylinder numbers, #1 is nearest the windscreen(back of engine), #6 is nearest the radiator(front of engine).
Doe's your car have carby's or fuel injection. Carby's look like the pic below,they are on the right side of the engine.

so it would be number #5 and #6 the ones closest to the Radiator, Its is Carbys exactly like the picture.

I run Champion N11YX plugs, recommended from Repco's listing. Doug's write up on plugs below recommends Champion N12YC or NGK BP5ES, that may be a difference in our climates.

Doug or Grant will clear that up when they read this thread.


Are the plugs oily or sooty? If plug #5 & 6 are oily you have a mechanical problem, if thy are sooty the front carby is probably running too rich.
The pic below shows what my plugs looked like before the carby's were rebuilt and tuned.



Her is a couple of links to some reading on the topic.

Spark Plug and Ignition System Maintenance, Series III XJ6 XJ12 : How-To Library : The Jaguar Experience

https://www.jaguarforums.com/forum/x...17/#post928571 post #14 of this thread has a downloadable PDF.

When I bought mine in March it had the wrong plugs......I put a set of N11YX champion from Repco as Clarke has said and it was 60% better straight away.
The wrong plugs were also gapped at .045" which was wrong.
The N11YX plugs should be gapped at .025".