Reigning double Formula One world champions Red Bull finished the four-day pre-season testing session in Jerez, southern Spain, having completed just 21 laps after ending the day early on Friday.
It was the third day in a row that the Austrian team decided against running in the afternoon as they have struggled to come to terms with a series of technical regulation changes for the new season.
Australian driver Daniel Ricciardo completed seven laps early on Friday in the RB10, but was over 10 seconds off the fastest time set by Ferrari's Fernando Alonso.
"It's been a very difficult test," team principal Christian Horner said in a statement released by the team.
"We have had numerous Renault issues as well as chassis cooling issues, which have affected our progress. However, despite the lack of mileage, what we have managed to learn shows that the problems should be solvable for the next test in Bahrain.
"Part of the purpose of this early test was to learn about any issues ahead of the start of the season and there will now be a lot of focus on the dyno over the next few weeks."
The race is now on for Horner and chief technical officer Adrian Newey to come up with a solution before the next series of testing in Bahrain which begins on February 19.
There will be eight days of testing in all in two four-day blocks in Bahrain before the season gets underway for real at the Australian Grand Prix on March 16.
Red Bull's problems have been far from isolated amongst the four teams that are powered by Renault engines.
Caterham and Toro Rosso also struggled to complete a significant number of laps on the first three days in Jerez, whilst Lotus didn't even make it to Spain due to delays in delivering their new car.
By contrast, Red Bull's title rivals have made a strong start and seem well ahead of their preparations for the new campaign.
Mercedes' drivers Lewis Hamilton and Nico Rosberg have completed over 250 laps, whilst between them Ferrari and McLaren have registered the fastest times in each of the four days of testing.
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