Engine misfire and rough idling?

This sounds like a stuck or shorted fuel injector, to find out which one it is let's remove the spark plugs and look for the one that is black with soot, this will be the cylinder that is having the issue. Here is a generic guide to help you step by step with instructions in the diagrams below to show you how on your car.

https://www.2carpros.com/articles/how-to-change-spark-plugs

and please go over this guide as well which will show you the causes for the black smoke.

https://www.2carpros.com/articles/engine-black-smoke

MAKE
DENSO .................... FK20HBR11



GAP
Maximum gap for used plugs .................... 1.3 mm (0.051 in.)
Correct gap for new plugs .................... 1.0 to 1.1 mm (0.039 to 0.043 in.)

TORQUE .................... 25 N.m (254 kgf.cm, 18 ft.Ibf)

Check out the images (below). Please upload pictures or videos in your response to any problems so we can see what to help you with.