My 2013 XJ is difficult to start and smokes like anything. This happens in the mornings and after around 8 hours parked up. The smoke smells of diesel ( no coolant loss) once stated it’s misfiring for approximately a minute or so. Once cleared it starts fine every time and without misfire or smoke.

 

Welcome to The Forum! and congratulations on (what might be) your new-to-you XJ!
Have you considered getting that looked at?
Especially smelling like diesel, assuming what ever engine is in your car isn't a diesel.
If you expect to be active on the forum, or might have any questions on your car in the future, it might be worth visiting the NEW MEMBER AREA - INTRO A MUST forum, and adding a more detailed description of your car & location in a signature block or profile.
That would help anyone who might have something to contribute to any questions you might ask as far as whether or not it would apply to what car you have.

 

Russell, I take it that the smoke is white in nature? Is this correct? If so, you are more than likely looking at a bad head gasket. In short, some coolant is making it into the cylinder(s) and it is causing a cylinder or two to not fire properly, hence the hard start and then once you do get it firing, the coolant is taking all the heat from the cylinder and turning the coolant into steam (hence your "smoke"). these cars are prone to something like this especially if they have been run hot because of a coolant failure/bad water pump.

If the smoke is black, you may have the starting of a failing fuel injector. Granted, I would think that this would result in continuous black smoke, but maybe the catalytic converter is taking care of things once it gets up in temp.

Either way, I would think you need to have a technician take a look at the car and maybe have them take the car the night before so they can see the cold start conditions. this will help them out a lot. It may be a bit difficult to determine the bad injector just due to the fact that the catalytic converter is covering it up. But, the upstream O2 sensor may still be able to detect it. hard to say. Depends on how bad the problem is.

 

You don´t mention that you have an Diesel or Gasoline engine? If you have gasoline engine and you get smell of diesel, there might be that somebody have added diesel on your tank and you need complete draining of your fuel system. Gasoline+Diesel mixture don´t burn well on cold engine, but do work somehow in hot. (normally diesel fuel do not destroy petrol engine, far more serious on vice versa)
If you have an diesel engine, i suspect that you have faulty high pressure fuel regulator, leaking injector(s), faylty high pressure pump or as simple as wronly mounted fuel filter. (fuel return pipe in wrong place)
If you live in area where the temperature are still under freezing temp, then i would say that some (or all) of you glowplugs have failed. (on direct injection diesel the glow circuit are needed for starting only in freezing temps, opposite like old prechamber diesels need glow circuit every start when engine is not hot)

Please always be specific of details. This will give you more precise ansvers.