I have a 1990 XJS convertible which starts up and runs well at normal speed. Before I got it, someone switched the Marelli ignition back to the Lucas and changed the fuel rail to a 1994. When first starting, the idle is too high (about 1500 rpm) which slows down as car warms up. The AAV seems to be working inasmuch as the air flow to the AAV, inside the air intake area, gradually subsides to virtually nothing) I can drive it, but when the car gets warm, the idle drops to 500 or less and sometimes stalls. If I simply let it sit after starting, the idle eventually gets to a point where the car will stall. When moving the car from park or neutral to a gear, it will experience a drop from about 900 rpms to less than 500. There's a sensor on the front right water rail that isn't hooked up, but I don't know what that is? I've taken the car to Jag mechanics, and others, but nobody seems to know what to do. If you know a good V12 mechanic around Orlando FL or Greenville, SC, please let me know. If you have any other suggestions, they would be welcome.

 

Firstly, welcome to the Forums.

When the beast settles, please do an intro in the New Members Area.

Not knowing the specifics of the Lucas update, I will go with the basics.

Throttle bodies are full of Black GOO, solvent soaked rag, wipe them out until CLEAN. Sometimes an old kitchen butter knife is required to CAREFULLY scrape that GOO out. Take your time here.

Reset the throttle discs and crossrods to spec.

TPS may be set incorrectly, thus preventing the ECU from recognising "idle map".

Base idle of the AAV is set too low, it is explained in the attached papers.

There is a stickie at the top of this section that I wrote a while back about a no start V12, but it also covers some of what you are experiencing.

Also, some light reading so you dont get bored:

AAV rebuild procedure.doc

Adjusting the HE TPS.doc

Adjusting the V12 throttle discs.doc

HE Tune up.doc

SETTING THE THROTTLE CAPSTAN AND RODS GRANT.doc

 

Millbro,

My XJS started developing similar conditions, but a bit on a milder side.

It initially idles at about 1100 to 1200 when starting cold. Then idle speed drops to about 700. But when fully warmed up (after a good drive), the idle at start up is erratic, varying from 500 to 700. It even stalled on couple of occasions. It does not bother me that much, yet. But eventually I would like to figure out how to make idle more stable when warm.(I did clean the throttle body, and also played/adjusted TPS.)

 

Thanks for the input guys. I'm thinking of taking off the throttle bodies and cleaning them and then taking off the fuel rail so that I can better see everything. Maybe changing the plugs and changing the injector hoses might be overdue. Thoughts? Suggestions? There's also a sensor on the front of the right bank that's not connected.. Would that cause any issues? Thanks to Grant Francis. I'll start to go step by step through those procedures.

 

All very much essential for a reliable car, and important if not done for ages. I suggest make a plan and work methodically through each item. Can you post a photo of the sensor, I am not sure which one you mean?

 

i am with Greg.

Age is now seriously against many items under the bonnet.

Work through the list VERY slowly, and methodically (Greg is 100% there), and finish one area at a time.

Wiring is teh death knock of any V12 now, so start at the beginning, ONE wire at a time, plenty of beer breaks, must keep the fluids up, and finish when its finished.

A snap of the sensor would be great, as your market got some weird stuff.

 

Hi Guys, here's a snap of the disconnected sensor

 

Isn't that one for the air pump system? can you post a not zoomed in pic.