2004 ranger 6 cyl 85K after tune-up cyl 4 misfires (304)and a general misfire on low revs (316)
my mechanic doesn't have an answer.

2004 ranger 6 cyl 85K after tune-up cyl 4 misfires (304)and a general misfire on low revs (316)
my mechanic doesn't have an answer.I'd say spark plugs and wires. But you just got a tune up.

What kind of tune up. Major? Minor? What exactly was replaced?
If plugs were replaced were they gapped properly? Try the old ones just for kicks. If that doesn't help then try the old wires too. Did he put anything on spark plug threads? On wires?