1989 XJS V12 furl problem

A good chance that your car does NOT have one. OBDll was not required by law until 1996.
Some manufacturers had there own systems before then.
I found the following web reference:

"Sorry fellas, the 1989 XJS has no onboard diagnostics at all. It only has a red feedback monitor hookup [with a blanking cap] back near the fueling ECU in the boot. It was used for mixture setup and that's pretty much it.
The trip computer fault code readout didn't arrive until 1992."
The trip commuter readout he refers was a way to get codes (after certain steps taken) to show up in the trip computer display.
For OBDll compliant cars .... the port has to be within 3 feet of the driver with full access .... usually under the dash
Helpful?

Check the fuel filter(s). Your long drive may have shaken dirt or old fuel gunk ("varnish") loose and plugged the filter most of the way. Enough fuel gets by to start the engine, but then it starves when you put it under load.

Jaguar Sensor, XJ6, XJ8, XJS, XK8, S-TYPE, X-TYPE, XJ40 ...

www.jagbits.com/jaguarsensor.php
FITS: 1993-1994 6.0 XJ12 AND 1989-1993 V12 XJS FROM VIN 157118 ON, 1994-1996 6.0 V12 XJS FRONT DAMPER .... LNA1622AA - MAP SENSOR ... C42166-USED - USED SENSOR COOLANT TEMPERATURE FOR FUEL INJECTION

Thread: 6.0 V12 XJS High RPM When Warm - Jaguar Forum.co.uk

www.jaguarforum.com/showthread.php?t=54266
Mar 3, 2013 - I recently bought a 1993 6.0 V12 XJS and when it is started from cold it runs ... to 1300 RPM so it wants to surge forward when braking which is strange. ...Classics · XJS 3.6,4.0,5.3 & 6.0; 6.0 V12 XJS High RPM When Warm ... You might want to adjust the aux (extra) air valve to bring the idle speed down.

I would start with a tune up, then isolate any symptoms other than lack of power if it persists, like rough idle, sputtering, jerking, engine trouble codes, etc.

I would get complete set of maintenance records for that one. 250k is alot for a jag especially a V12. That one is either running on borrowed time or has been meticulously taken care of.

Hi Gina.... Rough idle could be a number of things. The easiest and cheapest thing you could do is to replace the fuel filter. Usually they will run just a few bucks at the local auto store. If that doesn't do the trick, try to see if your car is smoking at all and try to determine if it is blue, black, or white smoke. Usually a blue smoke is oil, black is usually fuel richness, and white is coolant. White and blue are the most serious. If you are just burning extra fuel, you might need a tuneup consisting of new sparkplugs, maybe new sparkplug wires, new distributer cap, and distributor rotor. This might be a good time the change the oil and oil filter as well as check the other fluids such as transmission, coolant, and brake. Joe

Thanks for choosing Fixya!

oil sending sensor could be bad. I know a few different type of cars have trouble with the oil sending unit. They all pretty much do the same thing, "oil light comes on at idle and goes off as you drive". But on the other hand it could be a little more serious.

look for a vacume leak. black smoke means it is running very rich

Most probably is the crank sensor under engine worn out. )0 % trobleshut starts here.
Einar Norway