[xeroinfinity]

misfire could be the wires, the plugs, how old are they?
also an onjector malfunctioning can cause a misfire.

On the coolant,
check the oil for milky looking stuff, or oil in the coolant.
Sometimes the sensor gets an air bubble stuck on it and it'll throw the low coolant light especially after it was realy low.
Try tapping on the resivoir to knock off the air bubble.