Japanese authorities already intervened this year but it didn't prove effective long-term. Market nervous about further intervention, move is a snail's pace. Key levels: 163, 164. Possible they wait until after US nonfarm payrolls on Thursday; if that pushes dollar higher, they may act on Friday (US holiday, lower liquidity = more bang for buck). Long-term, more than intervention needed to turn yen around.
They haven't given a strong signal like last time. Pay attention to policymaker rhetoric for clear indication they've had enough.