They say the man was followed for 25 minutes as he drove in an erratic and dangerous manner from Greenhithe on the North Shore to Onehunga.
A police spokesperson says patrol cars held off from pursuing the car because of fears the driving would worsen.
He says officers waited until the man parked at DressSmart Onehunga and then approached the car.
The spokesperson says the man started swinging a spiked iron bar and was then tasered, pepper-sprayed and arrested.
A loaded firearm was found in the car, which had been stolen.