1998 4.0l xj8 sovereign, ever since iv had the car (since last November) i get this rhythmic knock from the valve area,always on start up, especialy cold, it goes as soon as i blip the throttle,would i be right in thinking its the vvt? was this car fitted with it?

 

I suggest you take off the cam covers asap and inspect the camchain tensioners on the exhaust cam drive chains. They need to be metal-bodied items. You might find they are broken, but even if not, replace with the metal items. It is an easy DIY job. Engines have been wrecked through ignoring noises from the cam chambers, as when the chain tensioners let go, valve timing gets lost and valves hit the pistons.

 

I renewed the top tesioners back in jan/feb with the metal tensioners

 

Mine does the same thing. All my tensioners and chains are new too.

I've been lead to believe it's the vvt's due to low oil pressure/volume as a result of increased clearances in my 135,000 mile engine. This may or not be the case, I don't know.

A local euro car mechanic said to replace the VVT seals and it may help. He and others here also suggested a thicker oil (15W-40) than the real thin synthetic I dumped in at the last oil change.