I would say your steering column is buggered, very common problem with EA's, replacement unit is from ED and will solve it for good :)
I have done two in both my EA's. 88 and 91 ones
Car's I have owned. First car purchased in July 1994, in order of ownership.
VC Valiant 245Hemi, 280zx Nissan 5 speed, 88 EA 3.9CFI,94 ED Gli X Chaser, 79 FC LTD, 351, FMX, 91 EA2 Fairmont Ghia, 1999 AU S pack, 2000 AU Forte, 1992 EB2 XR8, 2001 AU2 SR, 2002 VX2 Acclaim, 2002 VX2 Manual S pack,2003 BA XR6 manual, 2001 VX2 Berlina.