The water loss has been stopped, but upon cold start, it feels like half of the cylinders are not firing properly... seems to be water could cause it in cylinders, but water level stays at same spot. What could be causing such a rough start but withing 30 seconds after start it smooths out. Checked plug wires, but that seems it would stay rough. Any ideas? Pressure in cooling system is fine, keeps pressure for an hour or so after cut off.