The attack happened around 10:00 p.m. Tuesday.
In a news release issued Monday, police say the teen was stopped at a traffic light at Broad and Windrim.
Investigators say the doors to the victim's car were locked, but when the suspect approached and pointed a gun she unlocked the doors, afraid the man would shoot her if she didn't.
Police say the man forced the girl to drive to the 5900 block of North 21st Street.
There, police say, the man pulled her from her car in an isolated area and raped her. Police earlier said the girl was raped inside the car.
The man then fled, on foot, northbound on 21st Street.
The suspect is described as a black male, about 20 to 30 years old standing 6'2" tall and weighing 210 pounds. He had a light complexion, a medium build, sideburns and a skull cap. He was also wearing a light grey Nike sweatshirt, blue jeans and black gloves.
He also had a tattoo of a star on the left side of his neck.
Police are asking the public to take a good look at the composite sketch also released on Monday.
"The composite really shows a specific characteristic, that star tattoo," said Captain John Darby of the Philadelphia Police. "Somebody should know who this guy is."
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.