Mellisa Grant was travelling on the A5 Watling Street, in Brownhills, when the interior of the Vauxhall Corsa became filled with smoke and flames. She pulled over near a bus stop and was able to get sons Braidan, aged three, and Bradley, aged one, out of their car seats seconds before it was engulfed by fire.
The blaze was caused by an electrical fault in the heating system.
A shaken Mrs Grant, 27, of Watling Street, said: "I had the heating on full to demist the windscreen as I was driving and smoke came through into the car vents - seconds later fire just appeared out of nowhere in the cabin on the front bottom passenger side, all while I was still driving.
"It happened in seconds.
"I managed to get Braidan out of his car seat, but I couldn’t get Bradley out of his. The car was engulfed in flames so I threw Braidan away from us because I wasn’t going to leave Bradley.
"The car was going to explode any second. I managed to pull him out.
"I ran with the kids to the nearest house screaming for help. The car then exploded behind us as I was screaming. The family in the house took my kids in. I rang 999 - I think I was still screaming."
She said her husband Jaime, 29, a bank worker, arrived at the scene shortly afterwards.
"He thought we were still in the car because all he could hear was us screaming and the fire had set the horn off so he punched in the front window and cut his hand open."
She was treated at the scene with oxygen for the effects of smoke inhalation, but was otherwise unhurt. The children were also unhurt.
"I can’t get that image out of my head: the moment I was driving and I turned my head and saw the passenger side on fire."
Mrs Grant, a housewife, said the car had been serviced and had passed its MOT test hours before the blaze happened on Friday evening. She added that she was planning to inform Vauxhall about the incident.
West Midlands Fire Service spokesman Ferg Slade said: "We were called to reports of a fire in Watling Street, Walsall, at 6.19pm on November 26.
"Firefighters from Aldridge station attended and found a car on fire with the driver safely out of the vehicle. Crews used breathing apparatus and a hose reel jet to extinguish the fire and provided oxygen therapy to the driver at the scene who was understandably shaken up by the incident."