I was on the hi-way heading to Banff on the weekend. I was doing about 120 Km/s (75 MPH) and went to overtake another vehicle and boom it felt like I had hit a brick wall. The car jolted heavily, accelerator went dead, I saw the orange light on the dash and go on and off in about 2 seconds and then everything went back to normal.
I did not have time to see the message on the dash. All was well for the next 400KM. Once home I connected my scan tool and all I got was P1111, no faults recorded. A month or so ago I got a misfire code show up but I could not remember which cylinder it was on. could that be causing it?

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2001 XKR Silverstone (added by GGG)

 

P1111 is a status which confirms all OnBoard Monitoring Tests have been completed since the last memory clear. Always a good sign.

Assuming the 'orange light' you saw was the MIL, it's odd that no code was set.

I recall a similar power loss on my 2001 XK8 but it was over ten years ago and I can't remember if the MIL flashed. With my XK8 it turned out to be the first early warning of Throttle Body problems. A failing TPS can send a throttle closed signal to the ECU which has the same effect as taking your foot off the throttle.

Just a theory to explain your occurence but none of the 307 Viewers of your post so far have replied with any suggestions and this could get the ball rolling.

Graham

 

Excellent advice above. I would also take the opportunity to carefully check the black plastic accordion air duct that runs between the air filter box and the throttle body for cracks and splits in the accordion pleats. If your air duct is the original one, it is probably cracked in multiple places and allowing air to leak into the system. That could have been the source of your issue....

 

Definitely could be a coil or air leak problem. Check fuel trims to see if it's a leak, but having had a code in the past you've done yourself no favours by not knowing what it was.

 

year and model would help as would mileage. in many cases a fuel mixture problem can cause a misfire, but i would still like to know the mileage on your coils. some engines have a particular cylinder that misfires with a fuel mixture issue and this helps to know. i am not sure if this engine has this idiosyncrasy.

 

Might be a bit of a long shot but could have been your traction control kicking in if the car felt a traction loss due whatever cause. It does come in harshly depending on the amount of power you're applying at the time.

 

FIRST THING TO CHECK.....check and make sure the engine temperature sensor is connected snugly, it's located next to the thermostat tower and is installed on the crossover pipe (on mine, 1999 XK8). Mine came off last Monday and the result was the exact same brick wall jolting you mentioned and my temp gauge went to zero. You may have other issues, but make sure that connector is on tight.

What speed was I going when it popped off? 75 miles an hour while overtaking another car...