Great news!

I guess that's the flip side of a CAN bus, anything connected to it can corrupt the signals to anything else?

Did you have to check every component connected to the bus, or was there a clue which to look at first?

 

Thanks,
I measured can bus resistance at OBD test adapter connection and found 120ohms while it should be 60ohms because two 120 termination resistors in parallel normally. Next I disconnected the J-gate can bus connectors (one from Instrument cluster and other from ecu) and both gave 60ohms (from their single termination resistor, as one is in instrument cluster and other in ABS unit, behind ecu in the bus that direction). So culprit of not having 2 parralel resistors at readout obd connector could only be J-Gate thingy..😉. And it was👍.
So glad with this forum. I knew absolutely nothing about can bus just weeks ago and could find this based purely on info put here by enthousiasts!

 

Even in agriculture (US), we now have to troubleshoot to bus levels occasionally. I keep a termination block (they're cheap) with me as a spare for some things just in case.
Amazing in that it was in the shifter, until you think about it. A John Deere engineer told me it is so much easier to run a bus line (or two!) than run a wrist-sized cable for controls/feedback.

 

I’m sorry to revive this old thread, but I thought it might be useful to someone else reading this trying to track down a solution to this issue.

The culprit for this symptom that plagued my car when I bought it was the canister purge valve. - A cheap fix, and a common issue in some Ford emissions systems.

I didn’t see this mentioned in the thread. In my case it didn’t trip the check engine light - at first. When it finally did, I was able to find the problem.

 

Thanks for the info.
Makes sense!
As a inoperative fuel pump can give this stumbling by lack of fuel pressure, so can a vacuum in the tank opose the fuel pressure I guess?

Few posts above I posted J-Gate was disturbing the bus, and caused strange stumbling.
This was never proven but problem was solved once J-Gate CB was replaced.
Later however, the car became worse and even brand specialist could not access the busses..
The car ran, but did not shift. Displayed all codes and messages imaginable.
Months of struggle later it turned out to be an bad connection in fuse panel (inside, not at fuse) powering the TCM.
So TCM intermittend (and low) power, that is something not reported often..
All fuses were measured and voltage on them as well many times over again.
Only until I measured at TCM side of the loom it revealed itself.
Turned out that when pushing the fuse (box) with the measuring probe, the internal discontinuity closed by the force...So seemed okay.

in hindsight, it could well be that the discontinuity was occuring at high vibration initially. Taking TCM out briefly, and giving ECU confusion what to do (retard power)
On the bright side: Learned a lot about the car:-)..
And still am.

 

Thanks for the follow-up. I always look to see if there is a resolution to a problem and glad to hear when resolved.

 

in the sport mode with “D” selected, my ‘02 XKR has no trouble getting to 5,000+ (in every gear) before automatically shifting. No “J” gate manual selections needed. The car has to be in the “sport mode” though.

Z

 

was it the cats?

 

Not entirely.
it was more a symptom than a cause.
surely the cat was restricting airflow making things worse.
it seems to have been a combination of issues.
Intermitent power to TCM, which caused the confusion in ecu, and intermittent (undetected by ecu) coil failure.

Coil failure undetected by ecu means fueling of related cilinder continued, causing fuelttrims will have trimmed back maximum by lambda input, with detonation on other 3 cilinders detected and pre ignition cut back as well.
While unburned fuel still entering the cat, causing it to melt.
The intermittent TCM power input failure (fusebox connection) might have caused ECU to not detect the coil failure.
Otherwise I have no explanation.
Car was super reliable after fixing, and has gone to new owners long ago (it seems long)
In the mean time I have a litre of XKR more (since almost 2 years)
It is going on sale today.
For a sad reason unfortunately, not being cash related.

 

"The XK8 is great if you want that sporty look and the prestige of owning a Jaguar, but don't have a lead foot."

This describes me to a "T". I love the ride and luxury, without having to prove anything. I drive it to enjoy the comfort and luxury. It is a great deal of fun, and I get approving looks wherever I go. I bought a car that was rough around the edges for $4000.00 and have put about $7000.00 into it. It runs fine and gives me pleasure. I care very little what anyone else thinks.