Omega VE 2 duel fuel runs rough on petrol

[Sam79]

I didn't use my car for a month. May just be a coincidence but two Days Into driving the engine light came on as started running rough as if not on all cylinders. Upon restart the light was gone and it was fine. Since then whilst running on petrol it felt rough like not firing properly a bit shuddery whilst putting the foot down. The last two times I started it from cold it nearly stopped and the engine light Came on and engine sounded very rough. Upon turning off and restarting and the gas kicking in from petrol it runs fine ?
I'm unsure where to start or who to take it too in Perth It was serviced last week at Holden but made no difference. I don't think they did anything but change the oil. They mentioned a carbon clean would be good? Could it be as simple as this being he problem is when started and it run on petrol.

 

[blackve76]

Mine does the shuddery misfire check engine everynow and then joy of modern cars.

If its fine on gas but rough on fuel put a freash tank of fuel in and drive on petrol for a few days and see if it settles down