Takieddine Boudhane, 30, had been riding a motorcycle when he was fatally stabbed in Finsbury Park, north London, on Friday evening.
Scotland Yard said Boudhane was involved in an altercation with the driver of a white van at the junction of Lennox Road and Charteris Road.
The vehicle, a white VW Caddy panel type van, was found in Islington on Sunday and taken to a police compound, where a forensic examination will take place.
Detective chief inspector Neil John appealed for anyone who witnessed the altercation to come forward, including those with mobile phone footage.
“The driver and person believed responsible for this tragic matter is now the subject of a police manhunt,” he said.
“At this time I am unable to release any further information concerning the identity of the driver as this may hinder the ongoing police investigation.
“The incident itself appears to have been spontaneous and not connected to, or as a result of, anything other than a traffic altercation.”
The fatal stabbing of Boudhane, an Algerian national who had been living in the UK for about three years, sparked the Metropolitan Police’s first murder investigation of 2020.
Officers were called to reports of a man stabbed in Lennox Road at about 6.50pm on January 3.
London Ambulance Service also attended the scene, where the victim was pronounced dead at 7.42pm.
Although formal identification is yet to take place, Boudhane’s next of kin have been informed.
Labour leader Jeremy Corbyn, whose constituency includes Finsbury Park, visited the scene on Saturday, calling for better protection for delivery drivers.
“People should not be carrying knives. A human life has been taken,” Corbyn told reporters.
“There are a lot of people working as delivery drivers, they must have better conditions of employment and employers must take more responsibility for their safety too.”
Fellow delivery riders, who had gathered in nearby Stroud Green Road over the weekend, claimed that Boudhane had been a victim of a road rage attack following an altercation.
Sourin Aydi said Boudhane was his “best friend”, telling reporters at the scene on Saturday: “I can’t believe it, I did not sleep last night. He was a wonderful man, funny with a great sense of humour and always laughing.
“If you have a bike then you are a target.”
No arrests have been made and inquiries continue, the Metropolitan Police said.