Eratic idle helppppppppppppp!!!!!!!!!!!!!!!!!!!!!!!!!

[freddiehebert]

So wonder what you guys would check first or change. 1998 explorer engine with 1993 distributor with computer and wiring from mustang medic. have explorer fuel rail with injectors bbk 70 mm throttle body. Car runs fine drives fine, track days are fine has been driven to LA and back , So Lake Tahoe no problems driving. Commute in it a couple times a week.

Here is the problem car has eratic idle, sometimes will be fine idles nice and then other times has a surge up and down about 1000rpms almost where it will die than surges back up. This never happens constantly could change from stop light to stop light.
This is not a new problem it has been an on going problem just finally getting tired of it
Any tips would be great. Thanks in advance