Yesterday, while cruising at 50 MPH steady I felt a sudden jerk and complete loss of power. Reduced Performance / Transmission Fault came up on the dash. OH SH-T!!!! The car would barely maintain 20 MPH at this point. The EXACT same thing happened on the XK8 episode of Wheeler Dealers and I did just what he did. I pulled over and shut the car off. Waited a minute and fired it back up. No check engine light, no further issues. Drove the car about 150 miles from then on out and it never came back. Car ran like a top!

What gives? Just a fluke or am I in for something big?

Later today I'll put the scanner on it and see if a code is stored anywhere.

 

At this point it could be either. There are many people who have had an occasional "fluke," and some in which that fluke will turn into a problem. I had something similar. The fluke started becoming frequent. Got engine bank lean codes, restricted performance codes, and transmission fault codes. Took some time to troubleshoot, but in my case it ended up being the MAF ($50).
The changing out all the parts ended up being the easy part....knowing which part to change was the challenging part. Fortunately, other suggestions that were likely possibilities were maintenance items that my car needed anyhow around its 100K mile mark.
At no time was this ever a threat to stranding me as I could just restart the car and all was good. Let us know about any codes you pull. I would recommend keeping your scanner in the car and if it happens again pull the codes immediately.

 

Just pulled the codes and came up with the following:

P1111 Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage

So thats that.

if it happens again I'll change out the IAT sensor.

 

No!

Code definitions vary between manufacturers and sometimes even models and years. You need to cross reference the OBDII codes from Jaguar's charts in JTIS for your car. P1111 just means all the emissions test have run...it is NOT a trouble code.

 

FYI...your car will always show either a P1000 (self checks not done) or a P1111 (self checks done). After you disconnect the battery the P1111 will become a P1000 until you do enough driving to change it back to a P1111. Neither code will illuminate the CEL. This is normal.

Hopefully your whole scenario was just a fluke.

 

Ahhhh, that makes total sense! I recently failed my inspection because of code P1000. Per the mechanics recommendation I drove about 160 miles to eliminate the code. Hence P1111.