Every time I exceed 100MPH+ my car shuts down. No dash lights. I put it in Neutral and re start it but nothing again, just idles, I have to slow down below 35MPH before it goes again??? It was doing that last month and the dash lights would go on like a Xmas tree, it was the battery terminal, Pos was loose.

Now it does the same thing but no dash lights go on? Any guesses? 98 XJR

 

Insurance God?

 

Maybe it's afraid.

 

OK, instead of any guesses...
How about has this happened to anyone? Or is there a speed limiter on these cars? perhaps a transmission issue? motor runs but transmission will not engage until I slow down...

 

The speed limiter is set at 155 mph, so that's not it. Any codes or messages?

So the motor dies, but you can restart it, but no drive until you slow down?

 

Rather than guess, have you checked OBD for any remaining codes?
That'd be the first place to start

 

Sounds like the throttle is sticking closed and vacuum is keeping it closed.
There were TSBs as well as a SERVICE ACTION (303-S514) for this fault.

bob gauff

 

Most likely the Government.

 

Correct...

 

Do you mean that the dealer has to fix this issue for free?
Also how can the throttle stick shut if its doing 100MPH? Wouldn't the throttle be wide open?

 

I guess finding the Service Action. Vacuum will drop with an open throttle -- although what about the R?

 

Maybe failure of the second fuel pump?

 

+1 on the fuel pump issue. And the wiring to both of them may be failing too.
Vector

 

Where are the fuel pumps located? 98xjr..

 

In the fuel tank. And getting it out to change them is a small PITA.
There is a fuel pressure test tap on the injector fuel rail, so a test gauge with a short extension hose will allow you to tape the gauge to the outside of the windscreen and monitor the pressure while you exceed the NH statewide speed limit!

 

Actually he means a VERY LARGE LARGE PIA especially for somebody asking where are the fuel pumps. Try your dealer or a Jag indy close by. Barring that, JE Robison in Springfield Mass 413 785 1665 is an hour or so away at 99MPH! Maybe one of the NE guys can give you a better suggestion. In the meantime check the relays for the fuel pumps in addition to what Spark suggests supra.

 

There are a lot of guesses being thrown around, because there's lots of information missing. Here's some questions, everyone else add your own.
1. Where is the gas pedal when it dies? Wide open, partly open, closed?
2. Does it stumble first, or just shut off instantly?
3. What rpm are you at?
4. What lights or messages appear?
5. What do you do when it happens? List all the steps.
6. Are there any after effects? Does it run ok again?
7. Does it pull to redline under full throttle at lower speeds?

Answer these questions and you'll get more help. Don't think about changing parts until you've got a better idea of what's going on.

 

I agree with what both of them said! Size of *** pain has a lot to do with place you have to work, tools you have, and what else is going on in your life!

 

1. To the metal...
2. Just cuts out instantly, I feel deceleration right away.
3. Did not notice.
4. None.
5. When I feel deceleration I look at my RPMs and thats how I know my engine shuts down so I put it in neutral and start it up while car is going about 50mph
the car starts up, I put it in drive, rpms stay around 2000 but feels like my transmission is not responding, by then my car slows down to about 20 or 30 mph and the transmission engages and acts normal again and of I go...
6. no after effect, runs fine, back up to 90...
7. no.

 

The second fuel pump comes in at 3000 rpm I believe. Not sure if it takes over from the primary pump, or runs in tandem.
Have a look at the fuses and relays.