looking for feed back from anyone on this issue. 1996 xjs 2+2 4.0 , when driving down the road and I lift off the accelerator, the car maintains the speed, regardless of the speed I was going- 30, 40, or 50mph etc. When I brake to slow down, car slows down to that speed. If I come to a stop, car idles normal. I disconnected the Cruise control linkage to eliminate it successfully. Throttle body and cable seems to work normal by hand. Anyone experience this?

 

tiredeli,

Check the butterfly is really fully closing on throttle being shut. They are prone to building up a carbon ridge that prevents them snapping shut. Also check that throttle is snapping shut when pedal released. Do this check with engine running and an assistant operating the pedal.

Good luck

Paul

 

Thanks for your reply Paul. I assume i have to remove the air intake also. An additional symptom i noticed is that if i put it into neutral while at 30mph, the rpms climb over 3000 and i have to turn the ignition off and pull over to bring it down.

 

tiedeli,
did you ever resolve that problem I see no response,my1996 xjs 2+2 does exactly the same,checked all the minor stuff,no luck and just saw your post without a conclusion,
sticky situation

 

I have not. I spoke to the local Jaguar dealer and they firmly believe that it requires a throttle parameter reset via the PDU, which the have, however after many hours of trying they have told me that they do not have the appropriate software any longer for their PDU for this year and to look elsewhere to get this procedure done. Still looking locally in Buffalo, NY for someone who has the proper software. Thanks for asking!

 

Essentially I believe we are dealing with a high idle situation, which as I am reading is not all that uncommon with these cars.

 

tiredeli,going to try some stuff and if not going to Jaguar Toronto.
Let you know.

 

I have been looking locally without success for a garage with the proper equipment to work on this. Anyone know an appropriate jaguar garage near Rochester NY or even Niagara falls\ Fort Erie \ St Catherine's Ontario ?

 

The throttle body does frequently get gummed up and it won't close properly, so I would start there. It's the same as an X300 sedan, I had one and it didn't respond to cleaning, replacing the throttle body was the only solution and then it was fine.

Do you have an OBDII code reader? If so look at the throttle position at idle, it should be around 12%. With the car off, also see if it goes to zero. The sedans have a slack adjuster in the cable and that may be misadjusted. Not sure if the XJS has one though.

The reason for the software is if the throttle is replaced it will have to relearn where closed idle is, and if the ECU thinks that it is off idle it will not move the idle air controller. The orientation will tell it where closed throttle is. However, before doing that clean and close the throttle by hand to make sure that it really is going to full closed. I suspect it isn't.

 

No I have not. I have been searching for the right place to take it.

 

Did you ever get it fixed? I have the same problem.

 

Yes. The throttle cable slack adjuster did the trick.