Engine light on and wont go off and blows white smoke

What is your question?

My jeep blows white smoke out of the tail pipe when i start it but stops after a few minutes. The engine check light is on and keeps coming after being cleared 3 times by a shop. 2 times by a shop once by a dealer. The code says that it has a misfire on the 8th cylinder but it has only misfired one time, all though it was shaking like crazy when it did it. It also lost all of its coolant once but hasnt lost any since. I had the spark plugs replaced to fix the misfire and seemed to but the computer doesnt seem to think so. Unfortunatly i havnt been driving it as much as i used to because to protect it from people at work, (no respect for nice looking vehicles), i dont know if that has any effect or not but im clueless and dont want to blow thousands of dollars at a dealer to find out that its not what i paid for. Thanks for help