After almost giving up I heard that my problem might be the timing chain tensioner. The chain, guides and tensioner were replaced about 40,000 miles ago so I thought they should be fine.
To be on the safe side, I removed the valve cover and checked for a sloppy timing chain after the car had sat for 24 hours. The chain seemed tight.
To make a long story short, I replaced the tensioner and all is well.
This still amazes me since even without hydraulic pressure, the spring located in the tensioner seems to exert pleanty of pressure upon the chain.
Has anyone any ideas as to what happened here?
Like I say, all is well but know I'm wondering exactly what happened.