The incident happened along route 248 near Palmerton on Friday.
The suspect was driving a black charger with one blue strobe light.
Investigators say the fake cop asked for the woman's driver's license, registration and insurance three times.
She quickly drove off once he drew his weapon and threatened to use it.
The suspect is described as a man with a medium build who stands between 5'5 and 5'9 with a military style haircut.
He was wearing a black polo shirt with a silver badge that said police on it.
Police say his car also had damage to the front driver side.
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