A large-scale configuration interaction (CI) calculation using Program CIV3 of Hibbert is performed for the lowest 87 fine-structure levels of argon-like iron ions. We have calculated energy levels, oscillator strengths, and transition probabilities for all electric-dipole-allowed and intercombination transitions between the levels of 3s23p6, 3s23p53d, 3s3p63d, 3s23p54s, 3s23p54p, 3s23p54d, 3s3p64s, 3s23p54f, 3s3p64p, 3s23p55s, 3s23p55p, and 3s23p55d states of Fe IX in the LSJ coupling scheme. Lifetimes of the 3d levels are also determined. The calculations include the major correlation effects. We attempt to correct the inaccuracies in the CI coefficients in the wave functions, which would lead to inaccuracy in transition probabilities by applying a ``fine-tuning'' technique. The relativistic effects are incorporated by adding mass correction, Darwin term, and spin-orbit interaction terms to the nonrelativistic Hamiltonian in the Breit-Pauli approximations. The present results are in good agreement with other available calculations and experiments. We predict new data for several levels where no other theoretical or experimental results are available. We hope our extensive calculations will be useful to experimentalists in identifying the fine-structure levels in their future work.