Vettel retired from Formula 1's season opener in Melbourne early on after his engine dropped a cylinder, and the team is working on finding out exactly what went wrong.
The four-time champion also suffered software-related driveability issues, and Red Bull boss Christian Horner says his outfit is struggling to know why the problems were all on one car only.
"It looks like it dropped a cylinder for whatever reason, and we need to understand exactly what has caused that - whether that is through electrical or software or whatever," he explained.
"From Saturday morning with Seb, the power unit put up a real fight and there was no logical reason for it.
"The settings are the same [as on team-mate Daniel Ricciardo's car], both fresh engines going in.
"But it shows how finely things are poised at the moment."
RICCIARDO HAD TURBO SCARE
Red Bull's problems were not totally confined to Vettel's car, however, because Ricciardo had a reliability scare just before the race.
"We had a drama when he left the garage as the turbo did not work," said Horner.
"We had to get the car back in to reset the power cycle, and it seemed to come back to life.
"So there was a drama as we were going out to the grid, but that fixed itself and didn't reappear."
- Daniel Ricciardo