Cold start idles high at 1800 rpm, semi warm the needle bounces between 500-700, fully warm it idles at about 700, engine rattles a bit when shut off, feels like its retarded without the fuel. I've got the idle adjuster screws all the way closed, so something must be off....timing? carbs?

 

What kind of Jag is this, specifically?

Cheers
DD

 

Series 2 Xj6...I'm thinking maybe the butterfly is crudded up leaving the flaps a bit open?

 

I'm still learning the details of these cars, but my first guess on the idle is leaking vacuum lines somewhere around the intake.

The rattling noise I'd guess is telling you the timing chains need adjusting. Mine did when I first got my car (Ser III XJ6). After that it quieted right down.

Good luck.

 

So i checked the vacuum and there are no issues with that. Tried to adjust the idle adjustment screw and got no changes in the idle. Starting to think that the carbs are off...

 

What carbs are fitted, SUs or Strombergs ? By now, (i.e. over 30 years since the car was made), there is likely to be some wear in needles and jets, so best to get a rebuild kit and clean and rebuild the carbs so you know where you are starting from. Cellulose thinners is ideal for cleaning off petrol deposits and gum.