I have 96 Nissan d21 Hardbody, the idle goes up and down,it acts like a misfire but its not. what should i do?

I checked everything, i replaced throttle body with all the censors including the Air flow meter, TPS, and the Idle control valve and its still doing the same thing. it makes no difference changing the throttle body.if you have have any tips on how to fix the problem please leave a comment blow