91 Escort LX 1.9 surging after warming up

[ILuvCelicas]

My girlfriend has a 91 Escort LX wagon with a 1.9. Recently it started surging for no reason. For the first few minutes it's fine. At idle, it will rev up and down for no reason (not all the time, just sometimes). After it warms up, when just going steady, not stomping or letting off, it will start to surge like the throttle is disconnected then reconnected then disconnected, etc. If you floor it, you go no where, but the engine does not rev at all. If you let off, it will move, but it does not stop surging. The ATF is looking like crap so I am going to drain/fill that with a filter. I don't think it will fix the problem but it needs to be done. Does anyone have any suggestions as to what's going on?

[jnjd]

I had this problem. It ended up being my TPS (throttle position sensor) located on the throttle body. I hope this helps...