I have a 2003 XJ Sport Saloon with 62,000 miles. It's a So Cal, "garage queen" and was serviced up to 60,000 miles by the local Jaguar dealer in Mission Viejo. During the past two months I have experienced the motor shutting down six times.
Five time while driving the freeway here in L.A. and once while sitting at a light. Not fun while driving 80 plus on the freeway and losing power!
Each time it happens there are no warning lights, the motor just stops running, the tac drops to zero, hitting the gas pedal does nothing.
After pulling over to the side of the road the car will restart and go to "default" mode with a "transmission error" noted on the dash.
It is not throwing any codes. The eight coils and spark plugs were replaced but to no avail. Now we have swapped out the transmission control module to see if this will fix the problem.
Will have to drive around and see if this is the culprit.
Anyone else have any ideas on how to solve this problem?
Thanks in advance!

 

The transmission connector gets dirty that feeds the transmission ECU which in turn talks to the engine ECU effecting it

the connector on the transmission is a push pull bayonet connector that does not twist off but like a air hose

another thing may be the fuel pump relay opening up as it looks at the engine crankshaft sensor speed for enable

The face of the senor on the back of the engine reports to get dirty with metallic filings interfering with the sensor

The throttle position sensor is actually 2 sensors one for the engine ECU and one for the transmission ECU

The return wire on both should read 0..5 volts DC with the engine not running , throttle closed , and key to the run position only before starting

 

Faulty Throttle can cause stalling. My 2001 XJ8 stalled a few weeks ago after exiting the highway. The engine restarted but the display said ENGINE FAILSAFE MODE.

I started it a few times and the fault went away. I checked the ECM for DTCs (NONE).

I drove the car and noticed the engine seemed to vary RPM without any input from the throttle pedal.
The engine did stall a few times when I came to a stop but restarted immediately.

I removed a throttle assy from another parts car I have (AJ27) and installed it on the 2001 XJ8.

So far for the last few weeks the engine rums normally.

There was a recall for the throttles back in the mid 2000s but this was for the AJ26 engines.

There are also ways to read the THROTTLE DATA DOWNLOAD to see if there is RECORDER ACTIVATION for the throttle.
WDS or IDS is required for the info.

There is also a possibility that the ECM is OVERHEATING.
I already related the story about a car that had been 'bought-back' by Jaguar from a customer because it stalled at times and could not be diagnosed and repaired to the customers satisfaction.

The car was re-sold to someone and the problem persisted and I was tasked to repair it. I performed all the tests I could think of and I involved Jaguar Technical Hotline.
Finally Jaguar sent out a FSE (Field Service Engineer) and we worked on the car for several hours testing and test driving.
We removed the ECM housing cover to do some wire harness checks and the FSE leaned his hand on the ECM and jumped back holding his hand in pain.

The ECM should NOT be that HOT!!!!!!!!!!!!!!

He told me to get another ECM ordered and perform IMMO SETUP.

I installed the New ECM and configured.
Test drove and the ECM never got more than warm. (FIXED................YEA)

bob

 

Motocarman: Was there ever a reason given for the early throttle problem? My early VDP had the switch and no one could give me a reason ... later I was told they had more than one problem with the early TB's. Both mechanical (leaking) and sensor contact problems. The later TB's was sensors and I was told by my friend (parts manager) that the setup for replacing the sensors was not something Jaguar wanted done in the service department. They would send them back. They obviously never fixed the problem.


To the OP -- when you say no warning lights. Nothing -- the dash is dark?

 

From what I was told (through the mysterious grapevine) was that the throttle fully closes at times to keep the bore 'wiped' clean and that the sudden vacuum keeps the throttle blade closed with more force than the throttle motor can overcome to open it.

The newer replacement throttles (and the software upgrade that some ECMs can be configured with) would lessen the chance of the throttle becoming jammed by vacuum.

We simply replaced the throttle assys or reconfigured the ECM on certain cars with a specific VIN range.

bob

 

Have you noticed the ABS warning light come on? If you have change your transmission fluid and drop the pan.
I am betting the fluid is burnt and there will be metal from the clutch plates on the bottom of the pan. If so you need to
get the ABS computer model fixed right away before driving the car anymore. The soldered connections are defective it is
a very common issue. When the ABS module is bad it no longer communicates with the tranny to tell the tranny how fast the car is going
so the tranny doesn't know when to actuate the valves in the valve body resulting in the tranny burning up. That is why it goes into limp mode.
You probably need to have the tranny rebuilt. When you replace the tranny fluid only use Pentosin ATF-1 . It is the manufacturer of the OEM
lifetime (yeah right) fluid the factory used. The OEM name is Life Guard which cost 30 - 40 % more.
It took me a while to hunt that fact down a few years ago. Even if my from first hand experience guess is wrong changing the fluid at 60K is
a smart move and you can rule the tranny out before spending anymore money on diagnosing the problem. All those things happened to me
and since I fixed the ABS module and rebuilt the tranny and used the correct fluid the car runs like new and there are no more warning lights or
limp modes to deal with. Oh there was a company making dip sticks for the car too which is great because I can now check the fluid level and
the condition of the fluid with out draining fluid to look at the color. One more huge tip, when you drop the tranny there is a good sized round bolt
that looks like a giant oil drain plug called a galley plug on the engine above the oil pan level making it easy to change the gasket on with out spilling
any oil. It will leak eventually and you need to drop the tranny to get to it. So now is the time to do that too. I hope I have saved you money and aggravation
by learning from my experiences. I have the same year XJ8.

 

Motorcarman: So do you have any advice as to preventative maintainance that would stop the throttle body from going bad on a 2003 XJ8 with 130K on it?
Can I change the sensors or clean the throttle body and connections to prevent the inevitable? (Plus where are the sensors and how to replace them)
Thanks

 

Gregg -- motorcarman is talking about the early cars .. not later cars. The sensors are not available -- so you can't replace.

The design of the sensors is subject to dirt and/or contact corrosion .... I always recommend pushing the throttle through it's range many times to clean the sensor -- with the engine off obviously.

Cleaning the TB should not be necessary -- but there is a procedure.