with a hand held Jaguar code reader we can see on most models a misfire counter that shows if a coil is misfiring and how many times before it gets bad enough to turn on a check engine light. Coil break down is common and replace the one doing it, unless you have a v6 in a X or S type. Then if a coil is misfiring unter the intake manifold replaced all 3 coils as most of the labor is pulling up the intake not replacing the coils. Any time you close to a 100k replace the plug when doing a coil. And dont let it keep going as misfires are a big contributor to killing cats