Hello all,
I recently purchased a beautiful ‘97 Daimler Double Six with very low mileage. It’s a Japanese import so no rust and just excellent condition throughout!

I drove it some 200 miles back from where I purchased it and it was a seamless experience - the V12 pulling wonderfully. Around 5 miles from home the “exhaust temperature” light came on. I understand this is a warning light/sensor fitted specifically to Japanese specification models to warn of higher emissions but, more importantly, raised temperature in the cat.

The car has two cats. I’ve read online of this second cat overheating/catching fire Etc but I don’t detect any issues. I have a (albeit basic) OBDII reader which doesn’t throw up any codes and I took it to my local garage who also can’t find any issues, yet the warning light remains. Do I need Jag specific hardware to read the code? Perhaps it’s just the sensor that’s at fault?

Any advice warmly received! I THOUGHT I heard some misfiring when the car had experienced this 3+ journey but having fired it up today and done some very short journeys to and from the garage I can detect no issues. If it were misfiring this would of course be dumping excess fuel in the cat and contribute to the raised temperature. One suggestion has been to remove the Japanese cat and replace with pipes as this will still apparently agree with UK emissions.

Thank you in advance!

Dan

 

I would just delete the polishing cats.

Done to many twin plug, twin cat per side V6, V8 & V12 Mercs. (3 valves/cylinder.) M112 engine onward. Prior to M272 series quadcam coil on plug 4 valve/cylinder series.

Mechanics used to run every time a M275 or 285 engine came in for a plug change. 24 plugs LOL! At least they did 100,000 Kms before change.

 

If I recall the Japanese cars have only one set of cats in the downpipe, and no underfloor cats, unlike the North American spec cars. I'd be looking for the source of the high temp, rather than just removing the cats, as if you do remove the cats you'll have the check engine light on all the time.

The X300's are unique compared to just about every other car in the world, in that the O2 sensors that control the fuel mixture are after the cats, every other car is before the cats. I'm not sure how Jaguar makes that work, but they do. They also use a unique type of O2 sensor (Titania vs Zirconia).

High temps indicate the car is running rich, and would probably be a MOT fail without the cats to do the cleanup.

 

High temps are usually caused by clogged cats. Benz use O2 sensors before & after the cats to indicate cat condition. Primary upstream sensor/s obviously for tuning/engine management. Killing the check engine lights for the polishing cats is simple. Plug it into Jaguar's equivalent of a Benz STAR computer & switch them off if you delete the polishing cats.

This car with it's low mileage has probably done much of it's running in town, open loop under mixture enrichment. Not good for the life of cats.

Jaguar does have some proprietary OBD codes that some basic readers might not pick up/recognise.

Option ~ test & replace the cats. First test the sensors.

 

Thank you all! I wasn’t actually monitoring this thread as I’d mis posted but all helpful comments, thank you. Actually the warning light seems to have disappeared and after some extensive investigations using various OBDII software I can find no issues. I also took a reading from my temp gun on both cats when they were hot and they seem absolutely fine!

Think it’s likely the car hadn’t seen that much action for some time so the sensor was doing a funny. I’ll monitor it and see what happens in the future.

Moderators: feel free to delete this thread as you see fit!

Thanks

Filmscoreking

 

If it's anything like the Daimler I brought in from Japan, it just needs a good workout and to get good and hot. Mine was shipped from Japan to Vancouver, BC and I drove it home from there. It ran much better after going up the long grade over the first mountain range in from the coast. Amazing what 20km of driving at full throttle and gaining 1300m in elevation can do!

 

I'll believe that. My Dad's car had only been used for shopping trips (in his 80's) & was not behaving to my satisfaction ~ only got attention if I happened to be in the country. I found a nice long hill & ran it up and down at WOT, high RPM on the up. There were chunks of incandescent carbon blowing out of the exhausts on the way up & smouldering in the road. Once I could dislodge no more crud it ran beautifully.

The Japanese have little opportunity to give a car an Italian Tune Up & adhere strictly to the rules of the road. A very disciplined society.

 

Not just Japanese cars. My son has an Audi A3 Turbo diesel. Only his second car but he drives it like miss Daisy on short runs all the time. Hardly goes above 1500 rpm and then wondered why it had started to smoke badly. I took it out and thrashed it at high RPM for a couple of miles and it was fine and has been ever since. Some cars just need to have the crap burnt out of them every now and again. My 1968 S Type is given a good WOT as Glyn describes every now and then just for this purpose and it sounds glorious to boot.

 

I missed this when you first posted but have now moved it to the correct model forum and deleted four posts regading the original posting location.

Graham

 

🤔 I had heard that the AJ16 uses oddball sensors with 17mm drive, but I believe the V12 uses more conventional sensors with the standard 22mm.

 

titania was as common as dirt in the 90s

 

Thank you, Graham!

D