bad MAF, IAT, Cold start valve, bad tach, bad ignition components.
Could be a lot of things.
First things first....
When the tach jumps do you "Hear" the engine rpms change, or just see the needle moving?
93 Ranger Splash. Standard cab. 3.0 v-6, 5spd.
Mods: New engine and trans. Cluster swap with tach. New headunit and speakers all around. 4x4 front valance. Led turn indicator mirrors. Crystal clear head lamps. Clear corners. 5" driving lights in Valance.
Mods to come: 'stang seats, explorer console, window tint, flowmaster cat back, some mild port work.