I finally got my 83 XJS started by disconnecting the coolant temp sensor on the driver side front. It seems that once it started it ran great for about 3 minutes then it started to surge up and down almost dying each time and would not level out. I reconnected the coolant temp sensor then it started after some coaxing. I drove it around for about 6-8 miles and it ran with less then normal power, maybe half or so. It even had a little bit of a knock like it was not advancing timing or something. I know that is might be something easy, I was thinking maybe a sensor but not sure which one. I sure could use some help as I am speculating on everything that I do with this car.

 

Please anywho who has any ideas, I am listening. I replaced the coolant sensor on the left front side of the motor. Made no difference. It ran smooth for 1 minute 30 seconds, then started to surge up and down then dies. difficult to restart without pumping the gas. Any ideas?

 

I'm not sure any of this will help but there are a few known XJS problem areas you can look at:


Make sure the throttles are synchronised.

Do you have a voltmeter? If so, the throttle position sensor can be checked.

You can check for a clogged fuel pickup in the small surge tank

Have you checked the fuel filter?

There's a vacuum hose that runs from the vacuum crossover tube all the way to the ECU in the thrunk. Make sure it is connected and not damaged

If I think of anything else I'll holler. I'm still on my first cuppa. Post back for details on any of the above, if needed

Cheers
DD

 

For sale: 1983 XJS with HE 61k miles $1500.00. most frustrating car I have ever owned. Starts when it feels like it, Mostly on warm days.

 

@outdoorsy

Doug gave you some good general suggestions, which, based on the limited info we got to work with is probably the best we can do.

Did you work through Dougs list ?

 

Is that copied from the advertising brochure?

 

You'd think so by now. It's been over 6 months since Doug made the sugestions.

Don't give up Outdoorsy stick with it and give the guys more to go on if you can.

These guys do know a heck of a lot about the XJS, and are generally pretty hot about helping folk out.

 

These cars are tricky to begin with ....and old age often brings a "stack up" of multiple problems that are really hard to deal with in any fashion other than a deliberate, step-by-step approach....eliminating each fault as you go along. Eventually you hit paydirt.

It take the patience of a saint sometimes.

Once you get a Jag V12 dialed in, though, they're a real gem. All the "stuff" you fixed along the way contributes to a sweet running V12...and then they require only occasional tinkering to keep 'em up-to-snuff.

Outdoorsy, if you wanna have another stab at it, I and others will be glad to help.

Cheers
DD

 

check your spark plugs... my explorer had a broken sparkplug and it behaved as you described..

also, since you mention timing, make sure that the vacum advanced is sucking, that your distributor is secure and that your distributor cap is free of rust and well set... we recently has some similar problems with my dad's mercedes and it turnout to be the distributor had come loose and moved...

good luck.

 

Can you give me a better explanation of the vacuum tube that runs to the trunk? I think I should check this in my car. See my new post, so I'm not completely hijacking Outdoorsy's post. Sacrider

 

I don't want to sound off like a scold here but I've gotta suggest that owning a vehicle 10+ years old is pretty much guaranteeing that you'll either need a ton of money to hand a mechanic or be ready to work your way through the vehicle from time to time tracking down weird behaviors.

That said I think your problems are solvable and as you work through the systems you will gain familiarity with how it was designed and why it was designed that way and learn new ways to curse various unknown engineers at Jaguar and periodically marvel at their cleverness too.

So your car runs rough, but it DOES run. That's far better than stone dead from a troubleshooting perspective.

Fuel, Compression, Spark

Since it's running likely the compression is good but since it's cheap to buy a compression tester and it's easy to administer a compression test then start there. Rule it out. Compression is good? Yay.

Next check the ignition system and be sure that not only are you getting spark, which you seem to be, but that you're getting spark at the right TIME. Get a timing light and check your ignition timing. Timing is set? Yay. Timing is not set? Spark is intermittent? Well now, check plugs, wires, distributor, ~vacuum lines~ and work the problem from spark plugs back to the battery. Follow the path.

Now look at fuel supply. Check fuel volume from the pump first and see if you're getting enough. Back fuel pump = easy fix. Clogged fuel filter = easy fix. There are a number of things which effect fuel supply including air flow metering. You'll want to use a multimeter to confirm the sensors are working properly (checking for voltages or resistance is easy, finding what they're supposed to be is a little harder but you do it once and accumulate the knowledge and then share it places like here).

Finally, you find that a mouse chewed half through a wire running to the fuel pressure sensor and promptly died in the gas tank and your problems are solved.

-Sodium