Robbo

Fantastic. Thanks for the photo too. It helps me understand.

Oops - must have been after too many beers when I wrote that. It's the water pump that I have been told is a problem, not the fuel pump.

Every Holden and Ford I have ever owned has needed a water pump replaced at some point in its life and 150k - 180k seemed like a fair lifespan when I was told to expect problems with the H6. The repairer that told me about it was STechnics in Perth and I then spoke to my more usual mechanic, a semi-retired friend, who confirmed that if the water pump went it would be a very expensive repair because it is behind the timing cover.

Still, based on your comments, it sounds like a failed water pump at this stage is more of an exception rather than the rule so I will continue to enjoy my Liberty. Maybe I will spend a bit of money upgrading the sound system, if I can find where to get a plate that will enable it. I may raise another question on that later.

Thanks to all of you for your help.

I got fed up so I took it to the business that was supposedly the best non-dealer repairer in Perth. They spent 10 minutes checking everything, poking, prodding, connecting their meter. They confirmed that all 6 cylinders had misfired but could not find anything wrong.

It's worked perfectly ever since.

I will take up your observations with auto electrician and will add to this post when I have heard back. In the meantime if anyone has had, or heard of, a similar problem I would love to hear about it. My mechanic did some research and told me that he found this to be a common fault that some attributed to with an oxygen sensor and others to a faulty fuel cap (it's not a faulty fuel cap) 

The only consistent code is a misfire of all 6 cylinders. In fact last time they were the only codes. Previous times it has always been 6 cylinder misfires plus a few other sensors but never the same sensor twice