It could be either, but check the simple stuff first. I had a lot of problems with slow-speed stalling with my '99 XJ8 that got worse over time. I cleaned my throttle plate at the suggestion of another poster, and the car has not stalled since. You could well have a problem that is not so easily cured, but this is cheap and easy to try. I paid about $2.50 for a spray can of throttle plate cleaner (you can get them at any auto parts store). To find the throttle plate, follow the tubing back from the air filter. Where the tubing hooks into the plenum is where the throttle plate is. Remove three 8mm bolts, pull the cover back and you're there. Be sure to hold the plate open while you spray - on mine the deposits extended from the edges of the throttle plate to the opening of the throttle body. It took about five minutes to clean mine, and it was pretty dirty.Be sure to use a cloth to wipe deposits away. A paper towel can tear off and fall into the throttle body if the throttle plate closes while you're wiping (and the spring is pretty strong).

 

That was my ride you probably read about, and it was earlier this year in early May. You could also have mismatched pins according to a jaguar tech (FactoryJaguarTech) so check out this thread. I Cleaned out throttle body on mine, whole deal, and it hasnt stalled since (hadn't stalled 2 months before I did it either though)

https://www.jaguarforums.com/m_53864..._/tm.htm#53864

NOTE: There was a recall on the throttle body so make sure yours was replaced.

@ Brutal

Yo bro same here about 2 weeks ago, sucks massive #*$&! But please don't bestray we need great techs like you sticking around!

 

YOU KNOW I TYPED A PARAGRAPH LAST NIGHT ON THIS AND YES I WAS LOGGED IN A FEW HOURS AND YES I TRIED TO SAVE BEFORE POSTING BUT WOULDNT LET ME AND YES GOT THE ERROR MESSAGE.....IM REALLY BEGGINNING TO HATE THIS FORUM FOR THAT CRAP....

 

I'm assuming there was a recall on the 98 xjr throttle body also??? If so, how do you know if it's been replaced or not?

 

@ skanoski

I was told there was on XJ8, mine was replaced in 2005 at the collection in Miami, FL. I've no clue about XJR

Just so this isn't a completely unhelpful post heh, I would have a tech run your vin, they should be able to tell asap, FTJ (factoryjaguartech) did mine in about two seconds and told me exactly when and where it was done. Perhaps call the dealership and ask them with vin?

 

Sounds like a vac leak or throttle plate prob.

 

OK ILL TRY AGAIN, CLEAN THE THROTTLE BODY ON WARM ENGINE, KEY OFF WITH A TOOTH BRUSH AND CARB/THROTTLE CLEANER.
1, REMOVE 2 8MM BOLTS AND INTAKE TUBE
2. SPRAY TO SOFTEN BOTH CLOSED AND THEN OPEN WITH YOUR FINGER AND HOLD AND REPEAT
3. THEN SCRUB WITH TOOTH BRUSH WALLS AND PLTE TOP AND BOTTOM
4. SPRAY TILL RESIDUE CLEANED OFF
5. SPRAY THE PORT IN THE SIDE WALL TO CLEAN IT TOO, THIS IS FOR THE IDLE AIR CONTROL SOLENOID TO BYPASS AIR A KEEP THE ENGINE FROM STALLING.
6. BUTTON EVERYTHING BACK UP AND START THE CAR, HOLD THE PEDAL TO THE FLOOR TILL IT STARTS THEN LET UP, WING THE THROTTLE A FEW TIMES TO CLEAR THE CLEANER, WAIT YOUR NOT DONE YET
7 REMOVE THE PART LOAD BREATHER LINE FROM THE DRIVERS SIDE CAM COVER, TOP FRONT, BE CAREFULL SO YOU DONT BREAK IT. NOW WITH A SMALL DRILL BIT ABOUT 7/64'S MAKE SURE ITS NOT PLUGGED AND YOU CAN PASS THE BIT THROUGH CLEANLY, PUT THE HOSE BACK ON, OK NOW YOUR DONE. THIS IS CHEAP, EASY, AND THE BIGGEST BY FAR CAUSE OF STALLING ON THE EARLIER V8

 

Good tip!!!

 

If you have random stalling be sure to check the two knock sensors on the top of the engine. I replaced one of mine which was covered in cracks and the car has not stalled once since! I had tried everything else; checked all the connections and the relays, everything seemed to be in order so I was very stumped, until I noticed the sensor was quite cracked from the years of heat.