Hi,

About a month ago I replaced the head gasket on my ef fairmont. When I started the car it ran beautifully on both petrol and gas. It never idled on petrol before changing the head gasket. Actually it hasn't idled correctly on petrol since buying it. Anyway I was surprised and happy that it was idling on petrol and gas. For the last week it has now stopped idling on petrol but is great on gas just like it was when I purchased it. Any help would be appreciated.

Stan

Do an ECU reset. If it again runs great on both petrol and gas for a week or so, its likely your LPG is out of tune, and the ECU is trying to compensate by adjusting petrol values.