Dear All, I just wanted to give you an update of how this all ended..... Well, as mentioned I had no warning lights and I instinctively didn't want to change the cats in France. We limped home at 65 and after swapping could packs and plugs etc, there was no difference. In the end I phoned the legendary Billy Bellinger and took the car over to him. Billy and his Dad are geniuses. They finally traced it to a gap where the bonding had degraded by cylinder 6 on the plastic air inlet manifold. Basically the air inlet manifold on the roadster is made up of two halves sandwiched and glued together along the top and bottom sections. it appears that the immense heat that we have been having caused the glue to melt on one edge which affected the air /fuel mix going into cylinder 6 (which was running 40 degrees cooler tat the others). They glued it back together and although the car is fine, I've actually fallen out of love with it now.
I have had 4 Morgans and have been loyal to the cause, often turning a blind eye on build quality. The roadster has cost me at least £7000-£10,000 in fixing things that should never have broken in the first place. But when something as fundamental as an inlet manifold fails, it takes 2nd rate build quality to another level. The car is 6 years old; I even thought that perhaps I should trade it in for a new one, but as far as I know the new ones are equally as bad.
I will need serious persuasion to stay loyal - I think its time to move on
Thanks also from me Dave and sorry to hear of your experiences and expenses. Bear in mind that MMC likely have little to do with engines supplied built up other than specifying their logo on inlet manifold. Great plug for Billy Bellinger in finding the obscure fault. I have to say my four year old car has cost nothing extra in the 22,000+ miles covered to maintain its total reliability other than a rad change, which I was expecting to do anyway by way of an improvement.