A few months back i tried to use my heat and it blew out more cold then warm so me and a buddy did a coolant flush and i replaced the thermostat because it was over heating on longer drives after all that it blew out nice and hot air (which i need again because the negative degree weather) and it hasnt over heated since then temp stays normal i have also already done plugs and wires and all that good stuff to add to the problems i have a cylinder 1 and 2 misfire code that comes on and goes away after a few days but my 1998 xj runs fine no misfire that i can tell when i start it white smoke pours out for a few minutes then goes away but here recently it quit blowing warm air again and when it sits at an idle it runs a little ruff but then when you give it a little gas it runs just fine again im wondering if i could have a blowen head gasket or not or could it be the heater core this ? is a little akwardly worded i know sorry if theres anything else you need to know to help out let me now and its a 98 cherokee sport with the regular 4.0 automatic with 172500 miles

 

Everything you describe point to cracked head or possible head gasket.

 

could i have a blowen head gasket?

Could you? yes
Do you? probably not.
The "white smoke pours out for a few minutes then goes away" is more than likely moisture burning off due to the water "they" dilute our gasoline with. If you are really concerned about it, a compression test followed by a cooling system pressure test would be a good start at diagnosis.

 

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