From racing-live.com :

Fernando Alonso on Wednesday played down an engine problem that marred the track debut of McLaren's new MP4-22 car. The world champion did not refer specifically to the reliability fault in the team's official release, but to the newspaper Marca he expressed relief that the problem was not serious. Alonso pulled into the Valencia pits shortly after 3pm when the rear of his silver car began to emit smoke. "The oil tank was broken," he said. "We thought it was a broken motor but thank god it was only a little thing that cost us a bit of time."

Whoops - welcome to the Kimi curse at McLaren, Fernando - what if McLaren still haven't got the reliability sorted out ?