Kimi Raikkonen led the way as Ferrari maintained their advantage in the dry at Sepang in Practice 3 but an electrical issue for teammate Sebastian Vettel left the championship contender needing an engine change going into qualifying.
In a tricky session for the German, his best lap would be compromised by poor tyre preparation but the problem, which struck with four minutes to go, would be of greater concern as he cruised back to the pits.
The new engine being installed was set to be introduced in Japan but without enough time to find and fix the cause of the electrical problem the Scuderia took no chances and opted to change. It also now means Vettel has used all four of his allocated engines with six races to go including Malaysia.
As for the final practice session, Ferrari remains the team to beat as Kimi Raikkonen matched his best time from Friday to top the timings with a 1:31.880s, less than two-tenths clear of his teammate.
Daniel Ricciardo also equalled his mark from Practice 2 to claim third, just over two-tenths behind the pacesetting Finn as Red Bull continued to look the nearest challengers to the Italian team.
Mercedes took different paths in an effort to solve their problems from yesterday with Lewis Hamilton ditching upgrades brought this weekend while Valtteri Bottas stuck with the new aerodynamic parts.
The impact was negligible, however, with Bottas still almost half a second slower than Raikkonen in fourth with Hamilton dropping two-tenths behind in fifth.
On his 20th birthday, Max Verstappen had a scruffy session in sixth which included a collision with Jolyon Palmer at the final corner in the final minutes. The stewards are currently investigating to see if any blame should be apportioned.
A tight battle between Force India and Williams is brewing with Sergio Perez, Felipe Massa and Esteban Ocon all covered by less than a tenth of a second in position's 7-9. Stoffel Vandoorne completed the top 10, two-tenths clear of McLaren partner Fernando Alonso.
Renault appeared to struggle with Nico Hulkenberg only 14th and Palmer, who lost his brakes entering the final corner the run before his late incident with Verstappen, 17th.
Toro Rosso rookie Pierre Gasly was within three-tenths of Carlos Sainz, as the junior Red Bull team was sandwiched between the two Renault's in 15th and 16th respectively
Romain Grosjean understandably gave the kerbs at Turn 12 a wider berth after his crash on Friday but would spin at Turn 14 which compromised his session and left the Frenchman down in 18th in front of the two Saubers that completed the order.
