That car had a recall on the gas cap, do you know if it was done?

 

The harness connections to the TB have been an issue with my XK8. They became brittle. One broke up and the other had pin issues. I ended up buying the plugs with pig tails from Jagbits and soldered them in. The round connector to the throttle motor which I did not replace still gives me issues. The female end of the plug loosens up and I pinch it close a little from time to time to solve the intermittent warning lights. Checking the plugs to the TB and cleaning them is the best first step.

 

Does not fit the codes.

 

Did you get this issue resolved? I just joined the forum and am having the same exact issues with my 2003 xjr and wondered if you could give me some advise?? Thank you

 

What symptoms do you have? Describing your situation is best for you in finding your solution.

 

I pulled the car out of the storage and took it for the first long trip - 1000 miles to N.C. and back to PA. It worked perfectly, but at the end of the trip i got again dreaded P0455 and later P0172 + engine check light and Restricted performance. I re-set the OBDII and everything is back to normal. I could not find any vacuum leak anywhere- So, the OBDII scanner is a permanent tool in my dashboard locker.

 

I got the "Failsafe Mode" message today for a few seconds. I was at a stoplight so I cut the engine and restarted. Message went away...

Is failsafe the same as restricted performance?

 

most likely, Jaguar might have change it for newer models. My is 1999 and I get "Restricted performance", which does allow only 1/3 throttle

 

Early XK8s had an issue with the timing chains and/or tensioners wearing out prematurely. If you have the 4.0 liter engine in any Jaguar from 1997 through 2000 and the timing chains have not been replaced, this is something that you may want to have checked. This can cause the "restricted performance" warning to come on periodically because the timing is off due to loose chains.

 

I finally resolved my issue with the failsafe mode and it turned out to be the Throttle Body. My mechanic found a place that rebuilds them and guarantees them for life for about $1300 versus the dealer cost of $3000. I have had the car back two weeks and it is running great now!

 

Update on this issue. Sorry for the bit of a thread necro.

I've learned a bit more about this issue, and have learned to deal with it in a few interesting ways.

First off, the new leads did not work. They were cheap though, so I'm not too broken up about that.

What actually caused the issue to appear to go away, was clearing the codes. Every time I clear the codes, the issue will subside for a few weeks.

It isn't really a "critical safety issue" as the engine does not cut out, and in fact the code clearing can remove the failsafe issue without even stopping the vehicle. Given my current funds, this workaround is sufficient considering that entire months may pass without the issue occurring.

 

I decided to treat my 1999 XK8 the same way. I clear codes and then I can drive up to 1000 miles before the !restricted performance" pops out again.
I carry a scanner in the car, clear codes and drive the car.

 

Clearing the codes is not a problem; however, clearing the same code over and over is not a good practice. You need to address the problem and to do that you need to get the code. You have a Failsafe indication but what is the code?

 

yes, the code that comes infrequently is P0172 (I have already changed both down stream O2 sensors).

 

The P0172 can come from many things a blocked air filter, fuel system return blockage, leaking fuel injector, failing fuel injector and incorrect signals from ECTS, MAFS, IATS & TPS. For you I would be looking at your MAFS or your TPS. Do you know if your throttle body has been replace or rebuilt? As a shot in the dark I would do a reset on your car and see what takes place then clean your MAFS and if you had one to swap it out I would do that a new one is a little costly on a hunch. The throttle body on the 1999 MY had a TSB / Service Action Link http://jagrepair.com/images/TSB/XK8/...20Throttle.pdf You need to see if your car has been looked at and modified accordingly. I am on my second TB at 123000mi the last time it was rebuilt by ASI Link Welcome To Auto ECU Inc. I hope this helps.

I should also note a low voltage battery will cause situations like this, have it tested.

 

Gus, can you tell me how to check the codes if I was to buy a code reader? In fact can I get a reader at a parts store? Thank you

 

Yes you can get one at your local store; however, like most OBDII readers for less than $200 or $300 they do not read all your codes but will give you what you need. I use my $30.00 reader all the time. As for the codes I will direct you as best I can.

In my opinion everyone should have an OBDII code reader.

 

I had the same issue, replaced with brand new MFS . issue gone

 

I do not even know where to go on my car to find the codes? Is this under the hood or under the dash???

 

The plug for the OBDII reader is under the dash just above the hood release. The OBDII reader gives you the codes and you look them up on a chart that is compatible with your my car.