Kevin Magnussen was left looking for answers after a misfire triggered his early exit from Qualifying for the F1 Azerbaijan Grand Prix.
After striking reliability issues, the Haas driver was eliminated in the first phase of the three-part session on Friday afternoon.
“I'm not entirely sure, but I had some sort of power unit issue,” Magnussen explained.
“It could be electrical as well – just felt to me like some kind of misfiring, so it could be, I think, an electrical problem.”
Earlier in the day, Magnussen had been forced to climb from his car after a fuel pressure problem halted his progress in Free Practice 1.
In Qualifying, he wanted to continue his final flying lap but was instructed by the team to box to protect the Ferrari power unit.
He ended the session with a best time of 1:43.417s, a time recorded earlier on with the engine misfiring.
“It's a bit of a bummer, but the bright side is this Qualifying is for the main race, which is a big opportunity to move forward,” he said.
“If it had to happen in one, I prefer it to be this one.
“Tomorrow's the Qualifying for the Sprint race, and hopefully, we can see what we can do there.”
Magnussen's Haas team-mate, Nico Hulkenberg, was also bundled out of Qualifying in the first segment.
The German admitted he had a messy session, not helped by two red flag interruptions.
“But that's not an excuse,” he noted.
“The laps were not as clean as they could have been. I think Q2 was definitely realistic and possible, but small things prevented that.
“A bit of a front lock in one corner, the other corner, I think I caught a big tailwind or crosswind,” he added of where he lost the time.
“It was actually just, on each lap, one corner that made all the difference, so a little disappointed with that.”
Hulkenberg will line up on Sunday's grid in 17th, just one spot ahead of Magnussen, as Haas locks out the penultimate row.
Before then, another qualifying session awaits with the Sprint Shootout to welcome drivers back to the circuit on Saturday.
The outcome of that session will determine the grid for the F1 Sprint, which follows later in the day.