The Japanese manufacturer introduced the update at the Sochi event to prepare the new engine ahead of Honda’s home grand prix next week.
It was lauded by Toro Rosso after Friday practice but it was then decided to go back to the old spec.
This is because Honda believes there is more calibration work to do and the engine can be better matched to the chassis.
The manufacturer insists the change is not for reliability reasons.
“Having studied all available PU data after FP2, we realized that, although the performance was encouraging, there is still some work to do in some areas such as calibration and matching the PU to the chassis,” Honda F1 tech chief Toyoharu Tanabe said.
“We have decided to revert to the older specification PU on both cars for the rest of the weekend.
“We believe we can complete the work before the Japanese GP, so that we can run the new specification PUs on both cars from then on.”
Crucially, running the new engine on Friday has added it to Toro Rosso’s pool of available Honda power units.
This means Honda can work on the engine as it desires and then use it in Japan next week without triggering fresh grid penalties for the team.
Pierre Gasly and Brendon Hartley will still have to start the Russian GP at the back of the grid.
Toro Rosso has used the opportunity of reverting to the older-spec ICE to introduce a new turbocharger, MGU-K and MGU-H on Hartley’s car.