Hello, I normally hang in the x100 forum, but my question pertain to a '98 XJ8. I know, the XK8s and XJ8s have share the same 4.0 engine but I thought I'd keep like with like.

Right, so someone asked me to give a listen to their '98 XJ8 with 113,000 miles on it while I was doing some wrenching on another vehicle, sure. At low idle ( just after start up and after completely decellerating) there is a pretty intense tapping noise coming from the engine. Almost like a loose valve, but it immediately stops as soon as you give it some gas. The noise does not increase or decrease with engine speed, either it's present or not.

Would this be indicative of the timing chain beating up the secondary tensioners and then stopping said destruction under load? Only to resume when not under load?

Thank you.

 

If it's not a SC, might be the VVT, same area as the chains.

 

That was my initial thought, VVT. But I wanted to rule out certain doom 1st. Correct, not SC.
Other thoughts?

 

You can try to disconnect the VVT (left and right bank one at a time), and see if the ticking goes away.

I think, but you better double check, disconnecting deactivates the solenoid, and the ticking should stop of the VVT is the culprit.

It will surely throw a code, but that one can be reset with OBDII reader after re-connecting.

 

I would definitely pull both valve covers ASAP and rule out the plastic tensioners first.

 

+1 on the failing tensioners. It has probably spit the shoe and is pumping up after the oil pressure increases. Mine did that on the right bank within a couple of days of buying my XJ8. Tensioner inspection revealed the cause. If the shoe is gone you will need to clean the debris out of the oil pan. It can plug up the pick up screen.

 

VVT is clicking, like a valve tappet, not too loud, where a failed tensioner is a rattle, very different sound.
If you are not sure, presume the worst, and do as said, check the tensioners first.

 

It's loud, will recommend removing valve covers and doing inspection 1st.