The incident began around 7:50 a.m. Thursday in the 1900 block of Conlyn Street in the city's Germantown section.
The 31-year-old victim told Action News last week that she was putting her bags into her car, getting ready to go to work, when the suspect jumped into the passenger seat.
Investigators say the man threatened her with a chrome handgun.
The man told the victim to drive away, then told her he intended to sexually assault her while pulling at her clothes.
The woman crashed the car into a gas station sign in East Mount Airy and was able to get out of the car and run away at Chew Avenue and Washington Lane.
She ran to a SEPTA bus for help, while the suspect ran away.
The suspect is described as a black male, 19 to 22 years old, standing 5'7" to 5'10" tall and weighing 150 to 170 pounds. He was wearing a black or dark gray hooded sweatshirt and dark-colored jeans.
Anyone with information is asked to contact Philadelphia Police at 215-686-TIPS (8477), text a tip to PPD TIP (773847) or through PhillyPolice.com.