Vibrating coming from accelerator pedal

[savs91]

Hi all.
Last trip away hitting some decent tracks in the Vic High Country brought on this weird vibration coming from the accelerator pedal when the car is idling. Will do it intermittently when the car is in park, then shift into gear it goes away, then back to park it comes back. Sometimes the other way around when the car is in gear it'll vibrate and out of gear it won't. Got a local mechanic to look over it and he thought it was intake related, but all my hoses are connected and no obvious leaks. Dr. Google mentioned potentially bad engine mounts? Not sure how bad the vibrating has to be when the mounts are on the way out...
Got me scratching my head, as i have no bloody idea what it is! Any help would be much appreciated.

[DibbyDibbyDJ]

any strange sounds?

Could be a brokrn balance shaft belt?

[savs91]

Nah no other sounds! What other sounds come from a broken balance shaft belt?

[DibbyDibbyDJ]

sometimes you get a strange whirrring sound

[savs91]

Not that I can tell mate. Just that vibrating through the accelerator pedal which you can both hear and feel.