I recently bought a 2003 XJR that needs a good deal of work; mostly under the hood. It has a bad knock sensor on the right (driver) side of the engine and I installed one in the wiring harness connector which cleared the code but have not installed on the engine it yet. I'm planning to pull the blower and do a number of maintenance items when I do. (I've had the car about three months but have been busy doing other things. Hope to get to it in another week or so)
The car has a very noticeable valve noise when I put it in drive; though the sound in park is normal. As soon as I shirt to drive, (foot on brake) the clicking starts. I have removed the blower belt but that made no difference to the sound. I am wondering if it has anything to do with the knock sensor not being attached to the top of the engine? The car has fresh oil so it's not low. I am attaching the two sounds to this message. One in park and one in drive. The recording does not really sound as loud as it does by ear but you can hear the differences. Let me know if this is something usual with XJRs or is there actually a problem with the car. Any replies will be appreciated.
Thanks a bunch!

 

Couple of questions. Are you certain the noise is coming from the valve train (trying to figure out why engaging the trans/adding load on the engine would cause a valve noise). Could it be coming from the trans?
Is the noise present on cold start only/disappears when warm, or is it always present?

 

This recommendation may or may not give you anymore information but, with someone else inside the car, have them go between P & D with you standing on the D/S by the engine. Remove the oil fill cap and see if the noise is notably louder with it off vs on. Disregard the air movement noise of course, just focus on the noise itself.

 

Maybe actual spark knock? Sounds kind of knocky in the clip. The new sensor cleared the code, but its not doing its job of detecting spark knock and adjusting the timing advance if its not mounted...has it done this all along or is this new?

You're using premium fuel I assume, maybe run some fuel system cleaner through on your next refill. Maybe you have a hot spot in a cylinder thats causing detonation from carbon buildup.

 

Yes, trying to diagnose a sound like that is very difficult if we cannot detect where it is coming from.
Much more information can be had with the use of a stethoscope to narrow the area the click is coming
from. If you have adequate wheel chocks and emergency brake, it doesn't have to be a two-person job
Before I had a stethoscope, I used a broom handle.to locate the sound with good results.

 

Those are all good suggestions. Yes I did use a stethoscope and the sound seems to be coming mostly from the rear of the drive's sige valve cover. I am too hoping that the noise is being caused by the knock sensor not being attached to the engine block. If I don't see anything that may be the cause while the covers are off, I'll install the new ones and hope for the best.
The sound is there when cold or after it heats up. It's not really noticeable when the the engine revs up though. The seller said there is 87 octane in the car at this point so perhaps the combo of the two are contributing factors? I do have a can of Seafoam to put in the tank and I'll do that while I'm in repair mode.
I'll check with the oil cap off too. That seems like a great idea!
Thanks guys! Dave

 

With low octane fuel in there I'm betting this is just spark knock. The XJR is setup for premium only, not recommended, but required. Dump a can of octane booster in there to bring the octane level up high enough and run the low grade gas through and I bet this goes away.

 

Sounds very much like noisy injectors to me. My 01 had a similar noise before I flowed and cleaned them.

 

Yes I'm hoping it's just spark knock and I'll take that suggestion to add the octane booster and I'll also run the seafoam in there too just for good measure. Also K-Man, love the color of your car...I bet you get a lot of comments and stares with it...
Is it a red VDP supercharged? Best of both worlds!

 

Thanks, Just a run of the mill Carnival red XJR. People do seem to like it though. 👍
Also this is what I used to clean and flow test my injectors,
( )
It is a bit jank and I had to make an adapter out of a spare fuel rail but I was surprised at how well it worked. Not a great price for one time use but it looks like you have a few jags.

 

Yes I do like it too!
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Dang Dude! That is industrial! I might just buy a set af remanufactured ones if I think it's necessary!

 

I can name that tune in 2 notes.....