There are dozens (hundreds, actually) of reasons why a modern automatic car won't accelerate through its gears properly when you take off from a standing start. These can include sensors, wiring, fuses, mechanical issues within the transmission and even an on-board computer that has lost the plot.

While the Jazz uses a CVT transmission rather than a conventional automatic with planetary gears, the Honda still makes use of hydraulic transmission fluid to operate its torque converter and effect the gear ratio changes as you drive. So, keeping the correct grade of fluid at the correct level is critical.

In most cases, the best bet is to take the car to a workshop that knows this make and model and have it scanned electronically for clues about what's gone wrong. This will ultimately be the quickest, cheapest way to find out what's wrong. From there, you can make a more informed decision on how to proceed.

However, if you want to be a little more pro-active, there are a couple of things to try. First, check the level of the transmission fluid. If this is low (due to a leak) then the gearbox may have difficulty shifting gears or taking off at all. The other thing you could try is to disconnect the battery from the car and leave it for at least an hour before reconnecting the battery. This forces an electronic reset and could fix the problem. It's a bit of a long shot, however, and you may have to recode your radio and reset the car's clock.

It should be ok, but to be sure I suggest you contact Vicroads who will be able to put you in touch with one of their approved engineers. In turn they will be able to tell you if you would be contravening an ADR. By modifying the car you will affect the factory warranty in those areas you change.