Is this a Taurus? Make sure the distributor gear and cam gear are ok. Double check your installation and the cam gear.
Align No. 1 piston at Top Dead Center (TDC) of compression stroke.
Align locating boss on rotor with hole on armature, then fully seat rotor on distributor shaft.
Rotate distributor shaft so blade on rotor is pointing toward mark on distributor base.
While installing distributor assembly, continue rotating rotor slightly so that leading edge of vane is centered in vane switch stator assembly.
Rotate distributor in block to align leading edge and vane switch stator assembly and verify rotor is pointing at No. 1 mark on distributor base.
If vane and vane switch stator cannot be aligned by rotating distributor in block, pull distributor out of block enough to disengage distributor gear and rotate shaft to engage a different gear tooth. Repeat Steps 2 through 5 as necessary to achieve correct alignment.
Install hold-down bolt and clamp, do not tighten at this time.
Install distributor cap and torque hold-down screws to 18-23 in. lb. (2.0-2.6 N-m) , then connect distributor wiring harness.
Check ignition timing and adjust if necessary, then torque distributor hold-down bolts to 17-25 ft. lb. (23-34 N-m).