which is cylinder 4 misfire.

so now what should i do? should i test ignition coil? replace it?

 

there is only oh so many options.

first off, how old are your plugs? dirty plugs might cause a misfire. a misfire CEL only shows up after 14 misfires. And in one minute there is about 50 sparks.

most like its just a coil tho. people on here are selling for like $20 a peice. I would possible consider changing plugs as well if you haven't copper plugs are 2$ a peice at most auto stores.

If you replace that coil and your plugs and you still get that fault look at the wiring to the coil.

 

most likely is dirty/worn plugs.
sounds like general maintenance problem - might be worth an oil change and air filter too.