GDi Idle Problem

[wipash]

Hey guys,

My GDi is currently off having all its engine internals cleaned and/or replaced. I believe they're doing things like valve seals, piston rings, big end bearings, etc/ The garage has it all back together, and tells me that it runs fine, except

Sometimes it 'forgets' to idle, as in when idling it occasionally just stops.

It wasn't doing it before I took it into the garage. The garage supposedly can't work out why it's doing that, and so they're taking it to another specialist today. I don't particularly want to be ripped off by these guys, so I'd like you're opinions on what might be causing the problem, so that I know what he's talking about when he tells me what he fixed.

Any ideas? Maybe something he didn't plug back in/broke whilst the engine was in pieces?

If it's something that he would have caused I don't really want to pay for a replacement part so I want to know whether tha's a possibility, instead of him saying whatever it was 'had just degraded and failed coincidently while we were fiddling around.'

Thanks heaps!
Sean

[Subaru ETA]

Have they rest the idle stepper motor position? They need to disconnect the battery again to do a ecu reset then turn everything on like ac demister headlights etc. Let it idle for a couple of mins like that.

Or it could have an air leak?