96 ranger spits& back fires

96 ranger v6 dual wires,5speed, truck cranks ,but runs like on 3cyls, spits & back fires.Is it gas or timing

In newer trucks the computer corrects the timing. Pull off the ignition module and / or coil and get them tested.

If it hasnt had the spark plug wires changed I'd replace them and check or replace the plugs if they have over 75000k