Hi guys,


So, I have an intermittent problem With the 2000 XKR which is causing me major headache. Once in a while, the ignition cuts while driving. Typically, this happens at low or stable throttle while coasting on the highway. Needless to say not fun when engine stalls out at 60 mph.


When the engine stalls it is a clean cut without any warning; no sputter or hesitation. The display cycles through a number of error messages when this happens (transmission, ABS etc failure). No codes after the fact - none the wiser from using code reader. The engine will restart without issue after a couple-minute nap, but not right away after it has died.


My local Jag indie - usually quite a good one - tells me that this probably is a worn pot meter in the throttle body. Only way to fix is to replace the TB. Before going for such a drastic solution I would like to poll the competent crowd here - does it sound like the right move?


Viewpoints much appreciated!

 

Hi.


What is the mileage of your car?
The TPS (Throttle Position Sensor) will eventually wear out.
You also have a PPS (Pedal Position Sensor) normally trouble free.
A failing TPS will most of the time give you a failure code, but you need a specific Jaguar code reader, not a generic one.


Before getting a new throttle body which, as you probably know, is expensive, disconnect all electrical connections at the TB, spray carefully with an electrical cleaner (not WD40) and reconnect.


Also check/spray Throttle Motor Pwr. relay and Ignition Coil relay.


It could also be as simple as a bad ground connection.


ALWAYS disconnect battery when working on electrics

 

Throttle body or at least the TPS is a very good guess.

There was a service action (S514) issued for VIN range 001036 to 031302 for exactly the problem you describe . . . but that was for normally aspired XK and XJ models.

ASI has been used by a number of forum members for TB rebuilds.

ASI Announces Jaguar Throttle Body Rebuild Service | PRLog

 

Plug your OBDII code reader in the car and take it for a run and when it stalls check your code reader to see if it captured the code for you. Yes this could be a TPS but it also could be a knock sensor. First see if you can capture the code first.

 

Thanks very much guys - useful advice!


Gus: At worst it stalls once every other day, and at best every other week. If it is either the TPS or a knock sensor - would there be any way that I could provoke it?


Oyster: I did test with a Jag code reader at Sandberg, but nothing. I also had the TB and connections cleaned. You mention ground connection - did you think of a specific one or grounding in general?


What puzzled me was the clean and complete ignition cut, and all the funky error messages that come rolling in on the display. But if I understand you right, this could be consistent with a TPS failure?


The forum rocks!

 

Those strange error messages could also be triggered by a failed power or ground connection, so checking all connections beginning at the crimp of the battery cables, main power fuses and especially the bulkhead and engine/chassis grounds.

 

This sounds silly, I know, but the first few weeks I got my 2004 XK8 that happened several times, very scary at highway speed. It turned out that I had the steering wheel just a little too low and I had bumbed the key in the ignition switch with my knee. It didn't take much a of a bump to shut the ignition off. Every time roll to the side of the road, restart go through all the light sequence and then on my way. I have gotten used to the steering wheel a little hight then my 6 foot frame likes but have gotten used to it. Hope it is that simple.

 

Hi again.


TPS will usually fail on high mileage cars. We had a low miler at the UK forum who changed his TB to no help. Turned out to be a cheap relay, the Throttle Motor Power Relay.


It is possible to check the TPS. Complicated and time consuming, described in JTIS.


Electrical connections degrade over time, and these cars are getting old.
Battery clamps are thin walled and not very rugged. The wire going from the battery to the high pwr. protection fuses, become hot due to poor contact in my car.


A connection at the false bulkhead (fwd. right) have made problems.


There is a ground strap from chassis to gearbox underneath the car at the right side, which is exposed to the elements and tends to degrade.


In the TPS there are two parallel traces which are compared continuously, and a difference will throw up a code. (P0121, P0122 or P0123) I find it strange that you don't get any of these codes if it is the TPS.


Sandberg is the best independent in the Oslo area.


ALWAYS disconnect battery when working on electrics. But this will also erase previous stored codes.

 

Thanks - that's plenty of good advice to work from!


The TPS is starting to sound less likely, as the car isn't really a high-miler (70k miles), and as it doesn't show the TPS test codes Oyster is referring to.


Guess I will start by checking for poor connections/ground and hold on a bit on replacing the TB.


Daro31: Thanks for the tip, but afraid it isn't hitting the key.


Any other ideas and tips are appreciated! Particularly annoying with faults that are hard to replicate, and that don't show up on the code reader.

 

This problem could be caused by a number of things and that is why you need to try to capture the OBDII codes. The use of a code reader being plugged in and monitoring as the car is driven has worked for me and many others. Chasing a problem with no codes is never a good situation try to capture them.

As for the TPS & PPS on the throttle body they have a redundant system and when one is a little out of sorts (the readings are not equal) a fault will occur resulting in a code P1121 for the PPS & P0121 for the TPS. In the many years of reading throttle body problems I cannot recall one without throwing a code.

As for the ground that is entirely possible but I feel it would be throwing a bunch of codes and you are not seeing this. If you want to check the grounds to all points and the engine just pull the fuel pump fuses (keeps the car from starting) and take a lead from the ground terminal on the battery to the front of the engine compartment attach a digital volt meter to that lead then the other lead from the volt meter to the engine block. With the volt meter set on 12 volts attempt to start the car at the same time look at the meter and see what you are reading if it is above 0.50 you need to check your ground connections mine was at 0.06.

In the interim I would remove the ground from the battery and pull and reseat all the fuses and swap your relays with like relays. This process cleans the contacts and with the relays if one is bad your problem will be move to another location.