Since I've bought my XJR it has had a strange ticking sound.
The poor thing had been standing still for almost a year so I supposed it just needed some TLC.

Unfortunately the sound has not been getting any less.. It sounds to me like a ticking/tapping noise. Happens only on a warm/hot engine and is loudest at idle. It does rise with rpm but can't be heard above 1500rpm due to other engine noise.
Car drives normal and the sound isn't audible when driving, unless the revs drop below 1000rpm/coasting in neutral (automatic).

I've used a stethoscope to find the source, but dit not find an immediate answer since every component seems to resonate the sound.
It appears loudest form undeneath the car, but this might be due to the sound bouncing off the ground.

What I've tested so far:
- Flushed oil with fresh oil, drove a few miles and changed to 5W40 fully synthetic
- Pulled wires from coils during idle: no change
- No loud tick audible from any of the intake runners using stethoscope

Other problems I have which might be connected:
- Hanging idle (possibly due to badly fixed cable)
- Hard hot start (starts below 1000rpm while cold starts are at 1800 for a second)

The cam chains and supercharger have already been replaced with brand new units, so no chain tensioner rattle.

Been driving with it for some time now and it does not seem to get any worse or less.

 

I don't know about the supercharged engines but, the naturally aspirated engines all get 20W/50 oil. Maybe the oil you are using is too thin causing this noise??

 

I've read on this forum that 5W40 is acceptable for the AJ16.
Might change to 5W50 for the next oil change this weekend, but 20W50 seems a bit thick for the winter months?
I have no blue smoke or high oil consumption so the 5W seems fine to me.

What I forgot to mention:
The coolant temperature stays below half on the gauge. Already changed the thermostat, temp sensor, and temp switch but changed nothing. Car warms up quickly so it does not seem to be a problem with the thermostat.

 

20W-50 will bring balance to your life - you'll have the ticking on a cold engine, then, and I'm dubious it will alleviate any ticking on the hot side. I tried Valvoline 20w-50 in the early days of my x300 ownership, as we were just rolling into the winter months in N. TX, not exactly a frigid icebox - and the cold-starts set off quite a cacophony. I've long-since commonized on Rotella T-6 5W-40, originally utilized in the diesel Excursion, across my whole range, year 'round. You can check the owner's manual for recommended viscosity vs. ambient temp, but pretty sure you'll find 5W-40 ok across most conditions you encounter whereas the low-point for 20W-50 may be somewhat above your average minimum temp if you live in a place that is said to have "winter."

Throttle issue may be the return spring. There's a TSB (and I posted a how-to for a no-cost solution) but I'm not sure whether or not the supercharged were affected.

Temp gauge sounds normal enough, but to be sure you should get an OBDII adapter (gonna need one anyway, eventually) and read what the actual temp is as you drive. ELM327 BT adapter paired with TorquePro app on an android phone works (can be had for

 

Went to a jag specialist yesterday.
He told me that is was a lifter and nothing to worry about. So good news!

Already ordered some 10W60 oil since I've read on the forums that the car likes thicker oil.

He also told me that my hanging idle might be due to the IACV sticking, so I'm going to replace this and hope that it will also cure my hard hot starts and disappointing mpg (18mpg on almost only highway drives)

 

Dutch-R,

When your new oil arrives, you might try substituting 2 bottles of CD2 Oil Detergent for about 1 quart of oil. I've had good success with CD2 quieting sticking/noisy lifters/tappets.

Cheers,

Don