My 93 altima recently was having a nasty idle surge. As soon as i would put it in reverse it would surge to about 5krpm. This is scary considering it it hard to control this car when this happens. I changed the TPS and it seemed to fix this problem. Recently this being 2 months later it surged on me again to about 2krpm. This really only happens when in reverse. Firestone ran my comp, and they said I needed a new knock sensor. Is this accurate. A knock sensor causing a surge is hard to believe

Knock Sensor can not cause that.. please explain Little more on what the car is doing and i 'll see if i have any suggestions. Are you Driving when this happens idle? idle with foot on break.

i have seen engine's surge at idle when the throttle cable is too tight. It should have a little play.

GL :)