For some reason, my 2001 XJ8 has decided it doesn't want to accelerate. It will only make progress if the throttle pedal is slowly pressed. Any attempt at rapid acceleration leads to a lot of coughing and spitting.
I am old school as far as cars go, and despite this being my 4th Jaguar, I have never had this problem before. I had assumed that as in a carburettor, the throttle opened the butterfly on the XJ8 throttle body. This doesn't happen on this car. I have to assume now that it is an electrical function, controlled by a pedal position sensor and a motor somewhere.
Could someone help with this problem?
I have checked the air input and vacuum hoses and can find no leaks.
Thanks
Bill W

 

The throttle position sensor (TPS) does provide signals to the engine control module (ECM) that operate a stepper motor attached to the throttle plate.

The TPS has long been a problem source and until recently replaced only with the entire throttle body as a substantial cost. Now there seems to be a couple sources for the sensor.

https://www.jaguarforums.com/forum/s...solved-138182/

Or you might try cleaning the sensor:

https://www.jaguarforums.com/forum/s...ics-faq-50741/

The stepper motor has also been a problem point.

I meant to add that if you have throttle body problems you should be getting a CEL and OBDII codes. ??????

 

Whilst I had the air cleaner/throttle body Air pipe off I thought I would check the MAF sensor. The sensor wires are difficult to see. After cleaning, they resembled what looks like a small resistor. The centre third seems to have small lump on it with the outside thirds being clean wire. There seems to be 2 of these ??.
Is what I see correct or should they just be clean wire from side to side??


Bill W

 

Bill, how did you clean your MAF sensor? Once you've done this job it's good practice to perform a hard reset - cleaning the MAF gives the engine new air values and the throttle performs a recalibration, let the revs rise and fall and let it idle for 10 minutes to store the new throttle map.

If you have TPS or TPPS issues you'll know it by 'limp mode' not sluggish acceleration. The maf wires are as they should be.

 

I used electrical switch cleaner on the MAF sensor after taking it out. By hard reset I assume you mean dis the battery for 10 mins? Trouble is I have no radio code, so would lose the radio etc. What's the best way to find out the
radio code?

 

Old thread but by chance was this ever rectified?
I'm having a similar issue...

 

send the TB for rebuild

 

Personally, I wouldn't just send athrottle body with 50k miles out for rebuild without knowing what the issue was for sure.

 

with Vin in hand, contact any Jaguar dealer.