ok guys here is where Im at. I joined the jaguar ownership club. I have read for hours on this site. My wife says Im crazy. If you dont mind I have a few questions. the history on my car in unknown. all I know is the car sat for 7 years in a showroom. then 3 years in a garage. the previous owner said he added fresh gas and started it. tried to figure it out shortly and could not. the car idles at 1700 rpms cold and 1600 warm. i checked to make sure the contacts at the water sensor was clean and tight. i will need to change the plugs and fuel filter. i would like to know where to start with this. ? any help would be great. i did notice that the switch on the throttle cable is broken? thanks to all

 

Dear Worried,

You have too much air being drawn into the engine. Could be, among many things, the throttle plates and linkage need adjusting, a vacuum leak (or leaks) or it could be a stuck "AAV"-Aux Air Valve. The AAV is what increases the idle speed for cold running.

A V12 XJS is a fabulous car but sorting one out can be a challenge.....a challenge well worth the effort, I might add.

Many here will help whenever possible but I strongly suggest you read "The Book".....

Kirby Palm's Jaguar XJ-S Help Book

.....which is quite long (and tends to paint an overly bleak picture at times ) but it has info you'll NEVER find in any service manual. It's a fantastic resource.

If you want more specifics in the suiggestions I've made, post back and I'll elaborate...but it's all in The Book :-)

Cheers
DD

 

This website has a lot of articles on the Jaguar V12 - not manuals, just history etc from the "man who was there". Keeps ones spirits up when all seems lost !

WELCOME TO AJ6 ENGINEERING / AJ6 Engineering

 

thanks for the info. I downloaded the pages and read a few of them. So here is where im at now. I removed the air cleaner cover from the passengers side. I found the 5/8 inch line from the air control. I put a cork in it. I started the car and it idled at 600 rpms. great right? not really. the idle is nice. but here is where it gets odd. the car hesitates when giving it gas. the car also acts as thought it has a rev limiter built in when trying to hold the rpms steady above 2000 or so. this was the first time i had the car idleing for more than 5 secounds since I bought it due to the high idle issue. the top of the intake near the fuel rails the colant lines got pretty warm however when I looked inside the car the gauge wasnt reading any temp. so i looked around for the sensor. I found one at the water neck on the passengers side, and one at the area right alongside the air intake snorkle on the drivers side. I dont know what either one does. I also ran the idle bolt in all the way. I also noticed the mico roller switch on the throttle cable is broken also. i found the bushings on the butterfly shafts were also missing. on the back of the passengers side air cleaner box there item that goes through a grommet and into the air box., it had 2 wires on it and looks like a large metal pcv valve with an arrow on it. also I found at the air pump there was a vaccumm loke canister that had fallen out of the pump out port. i assume that had the same hardning or rubber grommet issue., I was hopeing to find the sensor that controls the temp gauge inside the car, as to noit overheat it. any othe info or guidence would be fantaskic

 

It sounds like your car has been bodged by a previous owner. If I were you I'd try to find an expert in these engines to look at it directly. We are a long way from you and these things are very difficult over the internet. You could try taking a few photos and posting these.

AFAIK, the mass air flow on these cars is via a vacuum tube to ECU, where the actual measuring is done based on engine vacuum. This needs to be OK and not leaking, also the fuel pressure needs to be within its limits. Forget tickover, you need the engine to give power, so check the ignition side, (which sounds OK), and the fuel supply.

There are no clever diagnostics on these 1989 cars, so it can be rather difficult.

 

Hello Worried,

I am sure you are excited with your car. Can you please share some pics of it on Jaguar XJ-S.

Regards,
dbk

 

You're in the USA so passenger side would be the right side. However, the hose you're describing (the AAV supply hose, if I understand you correctly) should be on the left side air filter box.

Did you put the cork into the hose right at the air filter box? If so make sure that you disconnect the distributor vent hose from the AAV hose or you'll suck oil up into the distributor.








That could be a throttle position sensor fault, vacuum leak, mis-adjusted throttle plates or throttle linkage, or...or....




You mean it doesn't want to go higher? If so, I'd suspect a fuel delivery issue...or, again, a possible TPS fault. If you have a voltmeter the TPS can be tested




I'm having a hard time visualizing which hoses you mean. There are no coolant hoses at the intake manifolds.





The sender for the dashboard gauge is on the right side water rail and has a single wire....probably green. There are other sensors for the fuel injection/emissions and, if you have Marelli ignition, the ignition computer.




Which probbaly didn't make any difference? If the AAV is stuck adjusting the bolt usually doesn't change anything




Transmission kickdown switch





You'll need to replace those






"Extra air valve" which increases idle speed when the a/c compressor is engaged






The diverter valve. Yeah, they often fall out. It's just a friction fit into the grommet





Sounds like your car has the typical XJS faults. There's magic cure. You'll have to fix alll the faults you find just to get back to square one and then, if problems remain, dig deeper. It's perfectly doable with money and patience. Continue reading the book. Everything is in there. We'll be glad to help as well.

It would be easier to help/answer if you'd break down questions into to separate postings

Cheers
DD

 

Doug you are amazing. What you typed makes alot of sence. I was wrong about the coolant lines on the intake. I read the book somemore and found they are the air injection lines. Boy they get hot. I gonna go play somemore

 

Not amazing, no. Just been there and done that :-)

When you're all done getting that XJS sorted out you'll be "amazing" as well :-). There's lots to learn but it's a really interesting and rewarding experience. I could never have done it without the help of others and Kirby's book.

Cheers
DD