I just noticed the same thing on mine this morning.
it was 5 degrees celcius and I drive 20 mins to work. I got to work and the needle had barely moved.
forgot to pay attention to it on the way home today.
normally it would warm quicker. I am thinking maybe because it was cold and thats all

not sure really how long they should take to warm up.
I know my idle changed quite quickly indicating it had warmed and was no longer in cold mode.

 

Well, I’ve dropped the Jag off for its second MoT attempt. Fate of course decided that on the drive to the garage the ABS light would come on, so I’m expecting a fail and some further investigation into that issue.

The temperature conundrum continues. It takes a very long time to come up to temperature, and if you’re on fast roads it doesn’t rise at all seemingly. Keep in mind this is during the British summer where temperatures have been in the low 20 Celsius range. In slow moving traffic it will eventually reach the centre of the gauge, but once you get back on a faster road the needle drops almost all the way back down to zero. I don’t think that’s typical. I’m considering putting the old thermostat back in!

 

First thing on ABS is to remove the wheel sensors and clean the face of the sensor different then the connector

10 mm and don't try too hard in pulling them out , plastic breaks leaving metal sensor cap in hub , not a cheap part

There is an alternate way to levering them out from the inside of the hub ( Motorcarman , Bob )

" but once you get back on a faster road the needle drops almost all the way back down to zero "

stuck open thermostat

 

Good news everyone, the Jag has finally passed its MoT! (With a long list of advisory faults…) Annoyingly they didn’t have a copy of the emissions printout, I assume if it passes they just bin it. I was curious to see how much they changed after my modifications.

Thank you all for your help with the emissions and the idle, now I get to enjoy the car as Jaguar intended until the next thing inevitably needs looking into. I may buy another thermostat just in case this new one is open too often, perhaps a slightly higher temp one if they are available. 90 Celsius instead of 88?

Next on the list will be new tyres, trying to get the AC working, and a few other QoL improvements. Generally though, she’s running pretty well.

 

Congrats! That was some effort.

i would add buying an OBD2 device that can also read ABS codes. Standard readers cannot pull those. It will also allow you to reset that light, should it come up on your way over to a MOT test, but what are the chances that would happen, right?

Anyways, spending some money on the right tool will pay dividends in the future, so I would strongly suggest prioritizing that.

 

A margin above 88 C thermostat as nothing is perfect in manufacturing maybe a 92 C

There is a climate control bite test to see climate control codes someone has made in this video

See page 110 for details

T703 BOOK (jagrepair.com)

 

i am swapping out my thermo (2 year old) for a spare 2nd hand tested working i have for this exact issue

 

@tobywood13 don't pass off the idea your thermostat might be dead/dying.
i took mine out today and tested it and found that it was beginning to open at 60 Celsius.
so in doing so the car was never getting warm.
the car was therefore being stuck in cold start mode and therefore running rich.

not sure when this started happening to me but it was very recent. and my thermostat is not even old.