I have a pretty clean 1993 Corolla DX with the 1.8 and 4spd auto trans. 140K. When I drive it things seem normal, everything is fine under cruising, but if I hit the gas while cruising at speed, the speedo needle will drop as soon as I hit the gas, headed towards zero, when I left off gas it goes back to where it supposed to be. How quickly/hard I hit the gas dictates how quick the needle drops. This causes the transmission to tweak out trying to downshift and do odd things, I'm assuming because all of a sudden it thinks its going slower. Other than that the tranny shifts fine.
I went to pick n pull and got a ECU, TPS, Speed Sensor, and a Speedo Guage out of another car. I've tried all 4 with no change in anything. I've also tried sanding and cleaning the ground from battery to tranny negative. I've also verified the throttle kickdown is correct. No changes in the issue. I'm pretty mechanically inclined and am need to fix this issue, the car is too nice to junk.
SOS please help!
PS I realize I spelled erratic wrong in the title, sorry.
