It doesn't matter whether you use up your turns you have to increase the weight - to use up the viruses turns. Plus they only go towards a node that you just activated. If you return to a node already active - it's like they don't see you.
Are you trying to hack into Helena's PC?
If so - spoiler below*********************
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Go Right, Right, Up and increase node to 4, then go Right, Right and increase to 4, Go left and increase it 2X, up - increase to 4, Rt, up and increase to 4, left, left - increase to 4, left - increase to 4, down, left, up - increase to 4, up - increase to 4, up - increase to 4, down, down, down - increase 2, up, up, skip a turn, up, right, down, right, up, up, right, action, left, down, down, left, up, up, left, left, action, right, right, down, down, down, down, left, left