stanza idles bad and engine heats up

[blackgoomba69]

I have recently replaced the coolant sensor and fuel filter that got rid of the check engine codes. but my stanza still idles bad and now seems to be overheating because smoke started to come out the engine. I've noticed black stuff on the ground, infront of the muffler, so i guess it's coming out of it.

What should I check first? :smash: