Check powertrain - engine cutting out

[Uldis Esots]

Hi guys, first time here and hope you can assist. I've had a VZ Acclaim for approx 6 months. Initially it had issues with the engine cutting out & check powertrain warning light coming on- I took it to a Holden dealer and they found a loose vacuum hose. Problem fixed. In the last month it's started cutting out again, approx every 200kms, usually whilst sitting at the traffic lights or at low speed. I took it to a Holden dealer and their checks couldn't produce any fault codes and road test couldn't fault it. A friend has suggested possibly a cracked exhaust manifold, although I'm guessing an injector problem or something electrical...any ideas? The problem has really only been at low speed or idling.
PS, the dealer has checked the oxygen sensor and couldn't fault it.

[andyman]

does the car idle rough? can you hear a vacuum leak at all?

[Uldis Esots]

No...the car's idling perfectly. Went for a drive of approx 200km yesterday on country roads with no problems. Also can't hear a vacuum leak.