I have a 05 xj8 L, and had this ride since new - just wanted to ask to see if anybody else has had the same problem I had the other morning,I was in stop and go traffic on the highway and all of a sudden the car pretty much shut,s down,the scare was the car wouldent accellerate at all,only 2000 RPM,and had a stiff brake.I had a hell of a time to get on the side of the road.I shut the car down and restarted and havent had a problem since.I'm pretty anil about the service on my car.Just wondering if anybody else had the same problem.I guess it's some kind of Fail Safe Mode.

 

Were you driving with both feet when the problem happened? Did you get any warning messages or check engine light? After you restarted the car everything was normal and still no check engine light?

 

I only use with one foot when driving,but my wife does use both of hers when she drives.When the car went into this mode all th gauge lights came on,stiff brake and only 2000 RPM with no gas pedal.Power steering was affected also.

 

What does left foot braking have to do with this?

 

No problem with left foot braking. The problem is with 2 foot driving, one on the throttle and one on the brake at the same time. What happens is that when you have your foot on the brake pedal at the same time you have your second foot on the throttle it is possible that the ECM will re-calibrate the throttle pedal position sensor while the throttle is slightly depressed and then when the throttle pedal is actually released it will cause a fault code for pedal position out of range. Any codes for either throttle pedal position or throttle position sensor will automatically cause fail safe mode. There is a software update that corrects this but most drivers use one foot and will never see the problem. The stop and go traffic comment prompted the question as that is almost always when the problem occurs.

His second post however changes everything. Having all the warning lights on and driveability affected to the point of power steering being disrupted points to a CAN network fault between modules. Also the fact that no check engine light or other warnings remained after restarting. Any pedal or throttle position codes would certainly have left at least the check engine light on. It's time for a proper code scan to determine exactly where the fault lies.

 

I can see were double pedel would be a problem,since this problem only happened twice,but almost got myself killed the second time.I,m glad that the Tecs found the problem and fixed it.Short in the Thottle body. REPLACED IT

 

Damn, maybe I don't want a more modern car *slinks back to the days of OBDI*

 

Throttle body.

The brakes felt stiff because the motor died. That is also why all those lights were on.

 

It's just the fly by wire thing. When you have computers in charge of the actual application of throttle you can't afford any errors. That's why there are 2 throttle position sensors in the throttle body and 3 pedal position sensors in the throttle pedal itself. They check against each other and any discrepency will cause automatic fail safe mode which fixes throttle blade opening and engine speed is controlled by fuel injector shut down from the ECM. Sounds scary but I almost never see any real problems with the system. Just wait until they have fly by wire steering if you want to be scared and yes it is coming.

I do hope that the new throttle body actually fixes Fast Jags car though. The biggest problem I see with the throttle bodys is water ingress into the throttle position connector and replacing the part may not stop water. I don't think I've ever seen an '04 or newer XJ actually stall, fail safe yes, restricted performance yes, limp home mode yes, stall no.

 

The car never shut off,It just gives you enough power to pull off the side off the highway,I just with they would come up a first warning before it shuts down,I'll keep you advised on my progress. Buy the way were did you get your brake rotors?