Hello Guys,

I have a 2003 XJR that I've been working on for a few months. I stared it a few week ago after I drove it perhaps ten miles. Then when I started it again a few days later it had this problem; when you press the accelerator, it revs up to 3K quickly but then drops back to idle and cycles through about one second of duration. Does not matter if you pull the throttle butterfly either. I checked it with my OBD tester and I did not get any reading about the TPS changing values which seems odd to me. Either the testor is unable to show there real time (which also seems wrong as usually i can monitor a number of signals live.) Does anyone have an idea of what I should check for? I would be very grateful as I've had this car for a while and would really like to be driving it!
I would like to add it's been a few weeks since this happened and I'm not sure if it will run good to do this again! Just too much to do these days!

Thanks a bunch! Dave

 

ecm has full throttle authority it just has a cable operated pedal position sensor. that’s just how toyota did their first ETC engines

are you doing this in neutral?

 

The engine rpm is limited to 3000 in neutral to protect the gearbox.

 

Put it on the road and see what she will do.

 

Well, what a dumb ***! That was unexpected! My 2000 VDP will rev beyond 3K so I suspected the XJR would as well. I did just drive it and it runs like a scalded dog! I guess one of these days I should around to finishing the rest of the problems....around everything else going on!

Thanks a bunch for replying....
Best, Dave

 

Don’t feel so bad, I learned something new a few weeks ago as well about these X308’s and I’ve been working on them for over 10 years now. XJR has what’s called a cool box auxiliary fan whereas an XJ8 does not (to the best of my knowledge). If you’re wondering what and where the cool box and this auxiliary fan is located.... The engine bay, passenger (right) side (LHD cars) underneath the little black tool lid is the top of the cool box where several modules are located underneath. Under all those modules is essentially a PC 3”or 4” (I didn’t measure) cooling fan. I’m assuming that the supercharged fuel injectors are high impedance and would create more heat inside the ECM and that’s why an auxiliary fan is needed?? This fan is actually located in the passenger footwell above where your right foot would rest. However.... I did run into an XK8 (naturally aspirated) that did have an auxiliary fan. So at this point, the XK8, XKR and XJR have this auxiliary fan whereas an XJ8 doesn’t??

 

It has nothing to do with the injectors. Sc engine makes so much more heat to the enginebay than na engine. Jaguar had fan in the same location in the sixties too.

 

Makes sense of the engine bay heat. Since the 60’s jags didn’t have computers, what was the reason for a fan in that location?

 

I do not know about the 60's but my (ex) 1986 Daimler Double Six had the battery (in a box) in that location and a cooling fan for it. The ECM was in the trunk so safe from any heat.

 

i think all of them have an ecm cooling fan

 

Interesting....It is great to see that we can still uncover hidden gems on this journey.

 

Along the same lines I recently found out that my 2014 XJ has small dedicated cooling ducts pointed at the back of the instrument panel as well as the back of the navigation unit. There is even a small fan assembly behind the drivers side of the dash dedicated to pushing cabin air just thru these ducts.

Only found out about it because people are installing after market Android tablets in the dash and some of them are failing from the heat but some of them don't. Turns out the Merryway units have you reinstall 2 PC boards from the stock navigation unit into their Android unit. This allows the car to turn the instrument panel cooling fan off and on. Without these 2 boards they fan does not run and things get HOT!

Since I installed the Merryway unit I never ran across this problem and had no idea even though had the dash all apart to install the Android unit. The fan assembly was plainly right in front of me when I found out about it.
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I had no idea that the Series III V12’s had a cooling fan for the battery.



This is not my Series III but, I have in my possession an 87’ I6 (original owner 152k miles) and I cannot imagine where an auxiliary fan for the battery would be located at in a cramped V12 engine bay. Just out of curiosity, can you edit this picture as to the location of the auxiliary fan is at if it was a V12?

 

You are right, there was no battery cooling fan with the v12 engines, only with I6. I sold my Double Six some 15 years ago so I had to think again of what I actually had. After I bought the car, I had a problem that a new battery died after just about 3-4 months and I noticed that it was getting very hot. I saw the battery cooling box in some diagrams so I thought the PO had removed it from the Daimler for some reason and I thought of getting one and installing it. I ended up just building a heat shield with a layer of insulation around the battery and that solved the problem.

 

For the last year of the Series 3 cars - 1992 - the battery was moved to the trunk and the Bosch ABS unit was mounted in that location with no fan in either location.