If it's Shiite vs. Shiite is it a civil war?
You mean, if similiar people fight, is it a civil war? Isn't that the definition of 'civil war'?
It's definitely a power grab, within the Shia community. Al-Sadr may be a thug, but he's no dummy. He knows that our election is close, our troops are tied down in Baghdad, and that the Iraqi central government is too weak to mobilize against him. Now is an ideal time to take his political power to the next level.
It's not a coup, per se, but it may be the start of a separatist movement, with al-Sadr setting himself up to be the leader of the Shia state. In his mind, now is the perfect time. Who's going to stop him?
Any war between sects of people in the same place is a civil war.