I have a 1990 Accord, AT, Any gentle throttle the car is fine, have to step on it and thats when things get interesting...

The pedal locks about halfway and the engine starts racing, and by racing i mean rocketing. Shut it off for a few minutes and the pedal clunks back to where it should be and the car is fine again.

The fast idle valve has been out on it for a while, ive not had the money to mess with it and only side effect is it revving in park or neutral.(Up and down)

Any thoughts on the cause or possible solution welcome.

 

Sounds like a sticking throttle cable. Unless its something obviously binding the pedal/cable such as a toyota floor mat, I would just opt to replace the cable. Make sure it is the cable itself, and not an excessively worn/sticking throttle body.