I recently purchased a 1990 XJS v12 with 28,00 miles on the clock. It runs great,however, it won't idle after the engine is turned off after it has come up to temp in Park. Cold start,idle no problem.

If you keep foot on throttle and put in gear, car functions normally until it is shut down and restarted while warm.

It may or may not be related, but, when car is started from cold there is a white wispy exhaust from left tailpipe and right tailpipe exhaust is clear. this goes away when up to temp. No coolant smell.

Underneath hood very clean and it looks like nothing has been touched other than oil change/air filter.

I have had 2 previous Jags a 68 E-type and a 66 MK 10.I do all my own work. But this one is a different cat altogether.

I would appreciate any direction in which to start looking. I suspect it is something minor and don't wish to turn it into something major through neglect.

The v12 is a beautifully smooth running engine and a real pleasure to drive and I would like to keep it that way.

Any help/advice would be appreciated. Happy motoring

Submitted by macd8905@bells… on Thu, 05/26/2011 - 16:09

it looks like the simple and free place was the solution. Installed new throttle bushings. One was gone and the other rotted in half. Removed and cleaned both throttle bodies, both were very dirty around edges of butterflies. Checked clearances,lubed and reassembled. Idle is very steady with engine warmed and up to temperature. The Hooray moment was short-lived though. As I was picking my daughter up from school, I passed a garbage truck going the other way and he was kind enough to flip a rock square to the middle of the windshield leaving a nice quarter size crack. So much for small victories. Anyone have a spare XXX windshield?
Thank You very much for you sage advice with my XJ

David

Submitted by dougdwyer1@com… on Sun, 05/22/2011 - 20:21

The sloppy linkage could cause off-idle problems but not idle problems. Check those throttle blade clearances and de-gunk the throttle bodies if only to eliminate them from the "could be" list.

Any of the usual Jag suppliers with have the throttle bushings.

Paper manuals come up on Ebay and JDHT (and some parts suppliers and perhaps even JCNA) sell the manuals on CD...which also include parts catalogs and the neat electrical guides. Sometimes they don't run well on Vista, though.

Cheers
DD

Submitted by macd8905@bells… on Sun, 05/22/2011 - 20:02

Sorry ,spoke too soon , it is still stalling but more intermittent. Drove the car around some and problem came back but it wasn't consistantly repeatable.Turned the bolt on AAV and nothing happened with idle. Returned to original position. Checked operation of idle switch also. It is good. Could it be that sloppy linkage on the left side without the grommet? No problems when engine is cold.

Submitted by No1inTex@verizon.net on Sun, 05/22/2011 - 19:39

Edited on 2011-05-22 19:40:49

Hey David,

I gotta butt in here and give you a hint. If your AAV does not cause an immediate response, you probably have a vacuum leak. A lot of the idling problems may be addressed here. There are a lot of vacuum hoses and as you well know, they tend to age, crack and cause this stuff. You will feel a lot better after replacing them, knowing they are not slowing down your attempts to make her as smooth as she can be.

Good luck, your posts make me think that you have a good grip on a great car.

Don

Submitted by macd8905@bells… on Sun, 05/22/2011 - 12:59

Checked coolant and it was a little less than a quart low. Topped up with distilled water and will flush and fill later. Problem went away, don't understand why, but I will take it. I guess I can call welsh and see if they have those grommets for the throttle linkage. Turned adjustment on AAV and didn't change idle much. Checked the two microswitches on top and they are functioning independent of wires. thanks for your help.
David

Submitted by macd8905@bells… on Sun, 05/22/2011 - 11:37

Okay first and easiest reply to your replies and thank you. Coolant level; how much is enough? Owners manual is useless in this regard. Can this be part of the problem? Come to think of it, coolant light did stay on for a brief period after startup. As for the other checks the throttle linkage has a rubber centering bushing missing on the drivers side linkage and looks a little sloppy ( where would I get one of those and whats it called) will check AAV, idle switch and throttle clearances this afternoon. Is there a decent shop manual out there for this ride?

Submitted by silver007@shaw.ca on Sun, 05/22/2011 - 11:06

just make sure the coolant stays up to correct level, and should be changed every 3 to 4 years normally. ....and use 20- 50m oil in Summer. Penzoil or Quaker State are apparently the best..... the synthetics apparently do not have the required additives for flat tappet cams....

Submitted by dougdwyer1@com… on Sun, 05/22/2011 - 11:01

There are lots of "could be" things but we gotta start somewhere, so.....

Here's a simple and free place to start: make sure both throttle bodies are clean and that the throttle blades are set to the proper .002" clearance.

(On general principles this would be a good time to check and adjust the throttle linakge rods that run from the throttle bodies to the throttle capstain. You want both throttle opening in perfect unison with just a hint of free play in the linakges.)

On the rear of the left itake manifold is a small snap-action switch with two very fine wires. This is the idle switch for the Marelli igntion. It should be closed at idle idle on open as soon as the throttle is opened just a fraction. I'm not sure if this would cause your problem but as long as you're rooting around you might as well check it.

On the left water rail, sorta just below the rear of the left side cam cover, is the AAV...Aux Air Valve. There's an idle speed adjustment on the valve. It looks like a bolt rather than a typical idle idle adjustment screw. Does the engine speed change when you make an adjustment here? I recall that counter-clockwise increases idle speed but I'm still on my first cup of coffee.

Cheers
DD