OK, so I am driving down the freeway heading to work in the XJR (2001), and I suddenly have no acceleration, along with ASC and Fail Safe mode flashing on the display. I get over to the side. Engine is idling, but there is no throttle response. I turn off the engine, then restart. Everything was normal; no errors or trouble indicators. This all happened 2 weeks ago, and it has not happened since. There has been no recent work done to the car that might make me suspicious. Cruise control was on, but not engaged.
Does anyone have any ideas??
Thanks in advance.

 

Sorry, meant ACS - I guess the dyslexia was kicking in...

 

Hi
You should probably have someone with a code scanner see if any DTC codes are still in the ECM. Since it went into the failsafe mode (limp home - engine controlled between 1000 to 2500 rpm).

I noticed that a TPS circuit fault (P0121) causes failsafe mode and turns off traction control & Stability - displays ASC/TRAC off warnings.

Jim Lombardi

 

That hapens to me today, Restricted performance and all other messages, P0121 on the tester. Engine stopps when the shifter was moved to N. Trying to start, it starts, but a little diesel-ing run with limited rev. Started again, no problem!
Any expert explanation?

 

Flay,
It will do no harm to clean both the throttle body and the connector to the TPS.
If that doesn't fix it you probably need a new TPS.

 

I remember that I did two things in that area: pulling the red tab from one connector on the TB trying to remove the connector, but I couldn't do it, and pushing with the finger the valve on the top of it (actually not me but somebody looking how I was cleaning the MAF with the air tubing off).
Where is the TPS and what is the part's code? Maybe it needs just a synchronization with a tester?

 

The TPS is on the side of the throttle body, probably where you pulled something off.
Make sure you've put it back properly!
I don't know this engine but if it's the same layout as a 4.0/4.2 then look in the XK8/R HOW TOs for cleaning the TB. Nothing to lose.