TbMn0.98Fe0.02O3 is an interesting multiferroic material, as the partial substitution of the Jahn-Teller active Mn3+ cation by the non-Jahn-Teller active Fe3+ has remarkable effects on the magnetic structure and on the electric polarization. This proposal aims at resuming the first experiments on muon SR in TbMn0.98Fe0.02O3, vs temperature and applied longitudinal magnetic field, to unravel magnetic fluctuations and disorder, and to study the effect of a static electric field on the coupling between ferroelectricity and magnetic ordering. This proposal is the second step towards a comprehensive muon SR study in this compound, involving the application of strong electric fields. By joining the muon SR results with those obtained from other techniques, we expect to disentangle the complexity and origins of the local magnetic fields, disorder and fluctuations, and magnetoelectric coupling.