Here's a link to the noise I'm hearing from my 02 XJR.

The engine sounds normal on startup, and perfect once warmed up. But during the warmup period, I get this noise. Most noticable goosing the throttle under load.


Any thoughts on what it sounds like? I've listened to videos of rod knock, and this sounds too high-pitched. I hope

 

Strange. The R doesn't have VVT, so that's not it. Doesn't sound like rods to me, it should be a consistent knock. It's sort of reminiscent of detonation, but you are obviously at small throttle openings.

It might be supercharger related. You can pull the SC belt off and drive it that way, but I just replaced my belt today, and it's a huge PITA.

Can you duplicate the noise revving it in neutral?

 

You can get the noise in neutral, but it's much less noticeable. Definitely more frequent and prominent under load.

I'm wondering if it's something in the exhaust system.

Can certainly try removing the sc belt.

 

I had to unbolt the SC belt tensioner to get the belt off, then it's a big hassle getting it back on. Don't tackle it unless you have time to tinker. 13mm for the tensioner, and a 1/2 inch breaker bar to release the tensioner to get the belt off.

Use the breaker bar first, then remove the belt off the pulleys, then undo the single 13mm bolt.

BUT, if you can't hear it coming from the front or rear of the SC while revving it from under the hood, then I'd suspect something else.

 

Was just out revving it up. While I can't get exactly the same noise in neutral, there are certainly some awful noises coming from the supercharger. A constant rumbling, that gets much louder when you rev it. Think I will disconnect the belt like you say.

 

How many miles on your car? To remove the belt a 1/2" breaker bar will fit in the square cut out in the tensioner. You can remove the belt from the supercharger and just leave it loose around the crank pulley. Then you can idle and rev the car in park.


It is much easier to engine internal engine sounds with the supercharger not turning. Also, check for anything loose in the engine compartment that may be moving especially the fan/radiator assembly against its rubber mounts

 

The car has 130K miles, so it wouldn't be a surprise if a few things were worn.

I just ordered a stethoscope from Amazon.

How much noise is normal from the supercharger? I can hear rumbling from it, that gets louder when the throttle is blipped.

 

At 130K the supercharger could well be ready for a rebuild. Once you remove the belt you can rotate the shaft by hand and check for a worn coupler or for contact between the rotors. With the stethoscope and the blower running you can isolate if the front snout bearings or the rear rotor bearings are worn. The front rotor bearings are the least likely to be the cause of the noise -if it is the supercharger causing the noise

 

The mystery continues. I have now tried the following :

Disconnected both belts, no change.
Checked compression, it is excellent : 145 to 155 on all 8
cylinders, cold, dry.
Checked first two cylinders for big end slack : nothing.
Inspected secondary tensioners : looks like new third gen
ones were installed recently. The parts are dated 2012.

You could eat you dinner off the inside of this engine.
Amazing for the age.

The noise sounds like it's coming from under the
supercharger.
--
2002 XJR, 130K miles. Also a Triumph TR8, 1980.

 

I wonder if the supercharger bypass valve is rattling somehow.

 

Hmmm, how easy is it to remove the supercharger?

Edit : you may be a genius. I occasionally get a P0400 code, which is incorrect EGR flow. I thought it couldn't possibly be related, but I just searched and found a reference to this being caused by a blocked supercharger bypass valve. Guess I know what I'm doing next

 

Go this folder. http://https://www.dropbox.com/sh/bwpyberv06lixgi/AAAlze1xzotirmaZ3C67BxyHa?dl=0
Have a look at the pics. Getting the EGR off isn't too,bad but the supercharger and the bypassvalve are a bunch more work.

 

Could it be just "engine knocking" under load (meaning combustion knocking that knocking sensor is supposed to catch and advance ignition timing)? Difficult to say from video, third time it sounded somewhat like that.