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Matt
Matt, Engineer
Category: Jaguar
Satisfied Customers: 380
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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What would make my 1988 xjs jaguar v12 idle fast and will

Customer Question

what would make my 1988 xjs jaguar v12 idle fast and will not slow down. It had been setting for 2 years I finally got it started today aand it idles 2000 rpm
Submitted: 1 year ago.
Category: Jaguar
Expert:  Doc. Jaguar replied 1 year ago.

This could de caused by several things. Do me a faver and remove the two rods going frome the center throttle tower to both throttle blads by the air filters. simply pry them off tith a small screw driver and see if it lowers.

Expert:  Doc. Jaguar replied 1 year ago.

Also, and I know this sounds strange, but is the bake fluid resivoir round and small (soda pop can size) or square and large?

Expert:  Doc. Jaguar replied 1 year ago.

This will tell me what ignition system you have. Lucus or Marelli

Expert:  Doc. Jaguar replied 1 year ago.

This year it could be eather or, as it was a mid-year chang

Expert:  Doc. Jaguar replied 1 year ago.

Allso where do you live? Are you in a area wher the tep. drops below freezing?

Expert:  Doc. Jaguar replied 1 year ago.

A OBD-2 scan tool will not help you as your Jag is a 1988 year. OBD-2 startted in 1995.

As far as making me a fav. I dont now. sent a e-mail to suport and let me know

Customer: replied 1 year ago.
sorry I haven't been able to view my messages as for the jaguar it has a Lucas ignition. I do live in a cold climate . I don't know a lot about jaguars but that being said I'm not completely incapable of figuring things out but it seems like to me that someone has played around with things before I got the car.
Expert:  Doc. Jaguar replied 1 year ago.

Remove both air filters and throttle linkage and set the throttle blades to .002 in. On the driver's side of the engine just behing the throttle blade you will find a hose going from the back side of the air filter to the idle control valve. On the side of that valve you will see the base idle adjustment screw. (13mm if factory 17mm if aftermarket) Run the adjustment all the way in. If it still will not idle normal at operating temp, that valve is stuck open and will need to be replaced.

It's bolted down on the coolant rail and as the coolant comes up to temp the air bypass should close.

If everything (tune-up related) is set and operating properly that idle screw should show two threads.