Lumpy idle, holding revs & hissing sound

[DM]

My wife's 2007 GTI has started idling really lumpy when warm, will sometimes randomly surge on revs, & when the engine is turned off I can here a hissing noise from the right hand side of the engine bay (As you look into the car standing at the front).

Any suggestions appreciated, as I'm a newbie here, more used to old aircooled VW's

[shoaybmakda]

Have you tried getting it scanned to see what faults come up?

[DM]

Will it show faults without and dash warning lights on?

[ChazGTI]

Yes it will. There will almost definitely be faults registered given the symptoms described.

[DM]

Cheers guys, will get it into my local garage

[Jaks101]

Check for damaged pipes to crank case and possibly a bad PCV valve (25£) part

[MIJ_JAGGER]

Check for damaged pipes to crank case and possibly a bad PCV valve (25£) part

^^this x2

Happened on mine twice, first time round was the pcv, second time quite recently was the pipe on that connects from pcv to under the intake manifold, cheap and easy fix 

[Saintsteve]

It could be the Diaphram that's split in the PCV valve assembly as it has a Pin hole in the side of it, which will Hiss air out of it and you will hear it especially when you shut the engine off.
HTH