Ok, the car is throwing codes about misfires. It SEEMS, but I can't say for sure, to do this under harder acceleration.

Car has 106,000 on it now. I'm just about to change plugs and plug wires - can I assume it's just old plugs and that this will go away after the work is done?

And here is something I don't understand - I don't feel any lack of performance. Is the car REALLY misfiring? And how does the PTCM detect a misfire, anyway?

 

Plugs and wires are definitely a cheap(er) fix to the problem, and likely the first source since no other code is being thrown.

As you've probably figured out, once one cylinder fails, the other ones usually fall like dominoes.

Try plugs first... unless you've had the wires on/off multiple times, I doubt they're bad. One thing about it -- if you do nee to change wires, those are super easy. The plugs are the PITA...

 

If you are gonna do this yourself Mark, in keeping with your new philosophy of not getting upset or excited :
Remove both valve covers !
Just a matter of a few screws, and the gasket is rubber so you won't need to replace it.
Leave the coil packs in place, just remove the plug wires and electrical plugs.
You will be amazed at how easy it is to get to all the plugs without losing several layers of skin.
Replace the plugs, put the coil wires back on the plugs, then put the covers back on and connect the packs.
( 'A' is the front plug of each cylinder, IE top coil plug to front spark plug )

 

With a Pentastar and even number codes you would be looking for the factory to replace the head (Chrysler had an issue with 3.6 Pentastrs in 11-13 models). In the XF I'd look to poor gasoline first with a P300 and ignition if confined to a specific cyl (e.g. P302). Can also be a failing injector since what the computer is looking for is a decrease in rpm when one or more cyl are supposed to fire.

 

Basically this means that the the car's computer has detected that not all of the engine's cylinders are firing properly.

A code P0300 may mean that one or more of the following has happened: Faulty spark plugs or wires Faulty coil (pack) Faulty oxygen sensor(s) Faulty fuel injector(s) Burned exhaust valve Faulty catalytic converter(s) Stuck/blocked/leaking EGR valve / passages Faulty camshaft position sensor Defective computer

P0306....Misfire in cylinder #6.