Hey guys! I apologize in advance if there is a thread covering this, but I haven't had luck finding anything. I am currently experiencing some preignition in my 2007 XJ8, and have determined that I will need to remove, disassemble and clean my cylinder head Anybody done this? Any knowledge, pics or threads would be greatly appreciated!!

Are you confusing pre-ignition with detonation? How do you know that you have either? These issues are generally unheard of on modern Jags.

Verified by two technicians, one independent and the other is a Jaguar master tech at the dealership. Spark plugs have been replaced one range cooler than stock, timing has been changed by a few degrees, EGR passage has been cleaned, two attempts with Forte products to remove carbon from the engine, and lastly the car will rarely throw a handful of misfire cylinder #x and random misfire codes. The symptoms are reduced fuel mileage (not terribly) and a very audible rough metallic clatter upon acceleration from a light after engine reaches operating temperature, also I can sometimes just barely feel it through the pedal when gears are changing at speed. Car is currently at 178,000km / 106,300 miles give or take a few. I can give you a brief run down of the car's last two years which may have contributed to this problem if need be

Nothing in your description points to pre-ignition or detonation in the least. Again, these cars do not typically suffer either problem.

If anything, the noise you're feeling and hearing sounds like it might be cylinder misfires caused by clogged catalytic connectors. There is considerable experience with that condition, our mod Cambo is a leading expert in fact. Maybe he'll chime in or you could send him a PM.

+1

and how did they claim to have changed timing???

I think they're out of their depth and now BS is the result.

Very interesting! I remember vaguely reading something about the exhaust system being responsible for this a while ago but didn't put too much thought into it. When I learned of the possibility of it being preignition I delved further into it. I will endeavor to over the next few days add a video of the dreadful sound as it happens and possibly OBD readings if I can manage!

EDIT: JagV8, I was not explicitly informed on the alleged "change to the timing" I have simply put together what I have learned from my own research with the brief mention and attached other customer story from the tech, that there was an adjustment made either electronically to the engine management program or physically via the distributor. I do not feign or profess to have any in depth knowledge (although I do wish to learn) about this car's mechanical or electrial systems so anything I say is free to be picked apart

Have you had the codes read?
Have you tried filling it with the best, highest octane gas you can get and taking it for an hour or two and giving it a good thrashing? My XK had a moderate acceleration rattle, good gas and a spanking fixed it.

Sounds very much like clogged/choked cats.

Happened to my XJR, and there are several other forum members who've reported similar problems, new cats and the problem was solved.

Feeling the love here guys! Cambo, woox4 I have definitely had that as a suggestion previously, switched up to Petro Canada's Ultra 94 for a few tanks and it did give a decent reduction in the sound produced under acceleration from stoppage. Admittedly I did recently have the throttle wide open (200km/h) for a minute or so. Hasn't changed too much, however I did have it chug and pop one day which produced a restricted performance message on the driver information bar. Was an isolated event in between the bottled product cleaning attempts. Moving forward, I'm assuming this would mean a replacement of the cat system? Probably out of my range of abilities if it involves welding

Well lucky for you, you're in Canada so you don't have to deal with CARB or the other restrictive legislation, and you're free to fit aftermarket catalysts to your car.

You can pick them up complete to bolt-in at (I think) are a reasonable price.

For example 2007 JAGUAR XJ8 4.2L V8 Catalytic Converter | RockAuto

No welding needed with those ones.

The octane rating of the fuel is not relevant as this is not a detonation caused event nor something that might have been affected by lack of good quality fuel additives. Your first two posts contained all the clues.

Where in Canada are you BTW?

Thanks Cambo! For a dual cat replacement, <$500CAD is a hell of a deal. Would you suggest anything else being replaced during this process as as a supplement to the overall health of the vehicle? Going from a battery of gaskets and replacement bolts for the engine plus any worn parts I would inevitably find and not feel 100% comfortable putting back in (personal flaw) to a cut and replace cat system is a bit of a relief. As much as I'm mechanically inclined and task oriented, doing a full R&R on my first engine ever being an AJ34 in my own car is still admittedly more than a bit daunting. woox4 I am located in the Southern Ontario region, maybe 2 and a half hours drive to the Rainbow Bridge border crossing?

With some effort the cats can be tested with a fair chance of telling which is bad.

Things like listening / IR gun / borescope.

I'm guessing the noise will be biased to one side of the vehicle? And by IR gun do you mean any run of the mill laser temperature gauge? As for a borescope, that I can't quite macgyver.. I have access to a very well equipped shop so doing some investigating is definitely doable. There may even be other helpful tools there to help determine what is the root cause of this. The prudent question to ask then would be where is/are the cat(s) located on this car?

I thought each spark-plug had an individual coil ?

That's correct and I'm beginning to doubt the capabilities of the shop the OP has been using. They may not be aware of the cat con problems but hokey cleaning procedures, changing heat range of the plugs and claimed timing adjustments demonstrates that they don't know pre-ignition from detonation. No excuse for that level of incompetence.

Another thing I've learned! Didn't know the car isn't equipped with a distributor, which I probably should have figured out by now considering how much time I've spent poking around in my engine bay As for the shops she's been to, the independent tech I most definitely agree has no idea what's going on, and the Jaguar tech I was simply inclined to believe based on his apparently hollow title.

Hi before replacing the cats have you tried a product called catclean had a few customers try it on there cars and they said it did make a difference and there engine light had gone off it my be worth a try before changing the cats

Thanks for the tip clifton94! The issue hasn't produced a CEL for any significant amount of time, nor has there been a drop in the car's performance so the issue is 100% just a sound thing. While undoubtedly it is causing damage to other portions of the vehicle, there is no outward indication of it actively happening. I very much appreciate the outpouring of knowledge and support from you guys; always nice to know there's a community of good people out there!!

UPDATE: I have found a friend of mine who is a welder and is willing to lend a hand! I read over many threads on people who have replaced their cats with 100 and 200 cell count units. Following the philosophy of why just replace when you can upgrade? I have decided on a set of Magnaflow converters, they suggest 99204HM which has no O2 bungs. After some searching I found that the 99064HM is the same 2" inlet and outlet, upstream and downstream O2 bungs, and is only marginally longer and wider. Any thoughts on this?