P0300 on your Jaguar X-type

P0300 means that the computer sees that the engine is misfiring. For an engine to properly fire, it needs the following:

1. Fuel: the fuel pump pumping the right pressure at the rail through the fuel filter and the injector injecting the right amount of fuel.
2. Air: from the air cleaner, to the throttle body, to the cylinder
3. Compression: good rings, compression seldom goes bad if you do your maintenance
4. Spark: the computer firing the coil and the coil firing the spark plug

If P0300 is by itself then the most likely cause is in the first two. If there are other misfire codes (P0301, P0302, P0303, P0304, P0305 or P0306) attached then I would diagnose those first.

So if it is by itself:

• Make sure the air filter is clean: Mann-Filter C 38 116
• The fuel filter is clean: Beck Arnley 043-1036
• You are putting the right premium gas
• The throttle body is clean: CRC 05078 Throttle Body Cleaner - 12 Wt Oz.