New to ford rangers myself, have been dealing with some of the same issues with my 86 2.9 EFI. One thing that helped is to get a code reader for your vehicle. In my case, an OBD-1. Most of the problems went away when I located a couple of minor vacuum leaks in hoses. I also replaced all ignition parts and filters and changed the oil. I go in for the smog test today so I'll see if I got it right...

So once you have read out the stored or active codes you'll have an idea which direction to go first. As you mentioned it could be several problems hiding in your package of symptoms. All I know how to do is find a place to start and keep picking at it until I figure it out. Code reader, shop manual, search the forums for similar reports and diligent patience...take notes too!

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86' Ranger 4x4 5spd 2.9L V-6