The Unit Racing Holden ZB Commodore had received a new engine for the opening round of the Repco Supercars Championship.
The issue reared its head in the opening minutes of Practice 1 at the Repco Mount Panorama 500, Kostecki suffering what he described as a “flat” engine due to a misfire.
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“We thought there was something wrong, but we kept it in there, we warmed the engine up, and went back out,” Kostecki explained, speaking with Speedcafe.com.
“It took a bit of time to fix so I think I did five out-laps and two or three fliers. I'm still new to the track, but we'll see. Hopefully we get some good running and do the whole next session.
“I'm a session behind and there's only two practice sessions, it'll be hard to get up there. Zane [Goddard] did the full session so we can use a bit of his data and look at what he did.”
Team boss Matt Stone said it was best to be cautious and not risk the engine's health so early on in proceedings.
“We just had a small misfire at the start of the session and because it's a fresh engine and fresh engine specs with the rings this year we wanted to be extra cautious so we brought it in,” said Stone.
“We threw a little bit of extra fuel in it to be safe and made sure we double and triple checked everything and when we went to go back out the red flag happened, so then we had to wait.
“It wasn't much of an issue in the end, we were probably just overly cautious with it. Jake was determined that the thing didn't feel right and we could see something didn't quite make sense.
“Once we tidied things up there was no real issue there so it was just really a new engine not really being one hundred percent.
“We wanted to make sure and it took us a bit longer than we probably would have liked it to.
“We had so many unreliability issues with engines last year that we didn't want to miss something and put damage to the engine and you fall back into that pattern,” he added.
“We just wanted to be super sure and then yeah we got out at the end and it was all running smooth. The car went out and was fine afterwards, we just lost that first part of the session unfortunately and when there's not a lot of practice that's critical.”
In all, Kostecki completed 10 laps, with his best time coming at the end of the session.
Kostecki's team-mate Zane Goddard completed 17 laps of the 6.2km course and was 20th on a 2:07.7831s, putting him 2.5775s off the leading pace.
Practice 2 at the Repco Mount Panorama 500 starts at 16:05 local time/AEDT.