A flashing cel is standared of a mis fire. You already no that though. Check your plugs. They should be light tan/grey. The electrodes my be shot. Plugs do wear out. They get very thin where they spark. This leads to them having the wrong gap(should be .44in) or even breaking apart. If the plugs are fine, could be somthing more serious. Was is starting to over heat? If so you blew a head gasket. If your powertrain is still in warranty you have nothing to worry about. Bring it in.