these xk8's have huge batteries in them. and i just realized that my battery is bad. thats the first thing im going to fix before doing anything else. maybe thats good advice for everyone

 

Good and sound advice!

 

So has there been any progress on solving the problem?

 

Sorry that I've been off the air for so long. All of you have been very helpful and I owe you an explaination. I've been just covered up at work and add to that helping out a relative in financial trouble that pretty much zero'd my available funds. So I haven't had the $ to do any further work on the car, and not much to report because of that.

But here's where I am today.

The car is livable, but not yet right. It still goes into Failsafe, but since I discovered that I could leave the key in "on" position, put it in "neutral" and then cycle the key through off and back to start - and it goes out of failsafe and actually starts just about every time. In fact there has only been one time in the past couple of months that I did that and it remained in failsafe. And even then only for another 5 minutes. So it's not stranding me, and if it's not stranding me for an hour or so every day - I can deal with it.

And from what I've been told, that is a pretty good indicator that I need to replace the rotary switch on the transmission, and that will probably correct this problem. It's on my "to do" list.

The other problem is the way it continues to run. On any given day, it may run fantastic, so smooth and powerful that you'd think the engine has been statically and dynamically balanced. Or, it may run terrible, with a lack of power and rough idle. Sometimes it will switch from good to bad or bad to good during the same drive. And I can find no reason or correlation with why it runs either good, or bad. I've checked all the grounding points (thanks to Bob for that information). And I've removed every plug, relay, and fuse and cleaned them, applied dilectric grease and reseated them. No difference.

So I've about made up my mind that I need to replace the ECM. There are what appear to be other indicators. The seat/steering wheel memory never holds it's program. It will work maybe 2 or 3 times, then loose memory. The windows are the same way. You reset them and within a couple of days they are back to needing reset again. So - a new ECM is on my "to do" list also.

In the meantime, I'm putting the car in the shop this weekend because the right front wheel bearing is noisy. And since they both rolled the same distance, I'm getting both replaced. And that's about the extent of what I can afford at the moment.

The car is livable. And a joy to drive - when it runs right.

Thanks all of you for your help getting it that way.

 

I recently had the Failsafe and engine cutoff and like you now I turn it off and it restarted with no codes and without trouble. I recently replaced the brake switch and waiting for the next time. I hope that when you find or eliminate the problem you will let us know. I will do the same!

 

I'll jump in here with a little advice on the ECM. I had a 97XK that had awful problems many of which were unrepeatable and random...but some of which seem to remind me of your devil vehicle (yes...I had one too). Ultimately it sounds like you may have more than one problem but I can tell you I fixed the majority of my problems with the ECM. If you take out the ECM and then open the unit up and see bad capacitors (what was wrong with mine) you will know you have at least hit on part of the problem. You can tell the bad capacitors by leaking fluid, discolored circuit board, popped top on them etc (it is the bigger capacitors that are affected). I rebuilt mine with new capacitors but it was a bit of a bear as the goo from the capacitors appears to be somewhat corrosive and eats away at the copper circuit trace.
Anyway...pop that bad boy (ECM) open and see if you have bad caps...I bet a nickel to a dollar they are...you can thank China for selling us lots of bad caps back in the late 90's and early 00's...same thing happens a lot to computer power supplies...
Ta Ta
Guy

 

Thanks for your insight into the ECM. It's always appreciated to know someone else has been there and done that, before you spend yet more money. But I'm not as talented as you and wouldn't begin to consider making repairs to the ECM myself. And since this car is my primary and only transportation, I can't really take a chance that I'd screw something up in an irrepairable way and have to wait for a new ECM to be delivered before I could make it run again.

But that new ECM is on my To Do list, just as soon as the holidays are done and I can afford it.

Thanks,
Oldfart

 

This is an update to my Failsafe Jaguar XK8 Throttle Body R&R I hope this helps!

 

Gus, thanks for that tip, but I already shelled out for a new OEM throttle body some months ago.

Since replacing the battery, and cleaning/dilectric greasing every relay, fuse and connector that can be found, the car was running better for a while. Still had a poor idle most of the time, but otherwise ran smoothly and started up most of the time.

It was still randomly going into failsafe mode. I discovered that if I just turned the key to the "on" position and pulled it down into neutral, it would start right up and run normally. So it was livable.

But lately that's no longer true. Now it no longer will start at all in Park but goes immediately into Failsafe, and sometimes it will not start in Neutral. Out of desperation, I discoverd that if I just pulled it through all the gear positions, then stopped in Neutral, it would start. But as of today it stays in limp mode and upshifts with a clunk between gears.

This seems to indicate replacement of the transmission rotary switch. So that's next on my list and I'm ordering it today. I have high hopes that this may exorcise the demon....but with my luck....probably just exercise the demon and make it stronger.

Any advice will be welcom.....prayers may also help.

Oldfart

 

What is a transmission rotary switch and how much is it? I have never heard of it, but maybe mine will break soon too!

 

Here's a drawing of the Rotary Switch from JTIS. It basically translates information from the shifter to the gearbox.

A bit more information is in the PDF below.

 

has there been any progress on solving the problem?

 

Welcome to the forum Vlad.

An intro in the new member section is always good and could be helpful to you in getting full access to the forum.

 

ive been reading the post from the gentleman in Hawaii but they just stopped Do you know what happen mr vlad. Email me directly @renaudsa@yahoo.com

 

did you get your problems solved?

 

Welcome to you Mudjag,

Continue reading here https://www.jaguarforums.com/forum/x...g-demon-74794/ then maybe you will want to post in the new members section which you will find here New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum