For YEARS I was plagued with constant non stop 171 and rest perf get ALL of that running perfect then this...My 04 XJR 152k all is GREAT, fuel pressure, NO codes or restricted performance BUT I am getting the strangest rattle almost ping noise at high r's right before shifting. Sounds like the engine is coming apart. BUT no knock sensors going off and these cars sensors are hyper sensitive, no cat codes, nothing. I am currently checking all rotating accessories. I already did the main belt power steering is TIGHT, water pump has MINIMAL plat, tensioner seems tight, now for the blower belt next, have you or ANYONE heard of this I am at my wits end. Can cats be rattiling if so I thought that would throw and efficiency code, im ready to sell please someone help me with this.

 

The only thing I can remotely think of, and it is NOT specifically related to the X350 R cars.

One of my V12's had that strange rattle/clang/ping. YES, I know thats a dinosaur compared to the Laptop on wheels technology in yours.

Way too many things changed etc etc, and eventually it was found to be the turbine blades inside the torque convertor parting company with the turbine.
I had the engine out, about to strip and search, when I remembered reading about covertor issues on these transmissions years prior. Off to the shop and furnace brazed rebuild, all silent from then to now.

Cat rattle, maybe, but I would think? flashing lights would be there.

 

Don't rule the cats out.

Meanwhile, check the fuel trims warm engine parked.

Also check each sensor you can for plausibility.

 

I have no way to check the trims and the cats would code wouldn't they>?

 

Why is this in the x308? I have an x 350 lol ?

 

Remove the S/C drivebelt and try again just to rule out the blower.

If you can get us a sound clip, that might help.

 

I did two vids yesterday how do I post them.

 

I upload to YouTube and share the link.

 

OK new info. Smoked the car fixed EVERY single leak, all with new rubber lines, got rid of ALL lean codes, car runs 100% until you rip on it then I get restricted perf, just check scanner i FINALLY have pending codes, the entire bank drives side random misfires 2-4-6-8 and codes po1214 and 1216 which is basically the rest perf kicking in. BRAND new coils great fp and plugs have 72k. 2004 XJRst check scanner i FINALLY have pending codes, the entire bank drives side random misfires 2-4-6-8 and codes po1214 and 1216 which is basically the rest perf kicking in. BRAND new coils great fp and plugs have 72k. 2004 XJR
ss have 72k have 72k. 2004 XJR

 

ONE whole bank misfiring I have to lean on injectors. I am getting pugs anyway but still now way can entire bank misfire from plugs.

 

Then you need the x350 section, they'll know more about that model than most people in this part of the forum.

 

His profile says it's a 1998 XJR but one of his postings says X350. It's kind of like an old
"Beach boys" song....you don't know what I've got....

 

As far as early 2000’s supercharged Jags is concerned, I’ll tell you that the X350 R cars are a pita to work on. The absolute worst R car to work on is an S-Type R. That engine is shoehorned in that engine bay like nobody’s business.

 

Sorry wrong forum I posted in 350 don't know how I did that lol.

 

No worry...happens all the time