I drove the Jaguar for about 30 - 40 minutes tonight. Everything ran great and smooth. Stopped at restaurant and picked up dinner, shut it off. Cranked, made what sounded like fan noise and then stopped and ran great coming home. Stopped at the our garage while my wife gets out and it goes rough idle and flashes traction control, stability control and failsafe mode. I pulled in the garage and shut it off. Went inside to get flashlight, waited a few minutes and cranked it again, all ok, no codes. Checked battery, 12.97v. I have no clue!!!!!

This is at least the second or third time this has happened in the last six months. I took it to the shop a few months ago on a wrecker because it did this multiple times in the same day. The OBDII reader showed a Throttle Position Sensor code. The mechanic checked everything out and did take the Throttle Body off and run through the parts washer for an extended period. It ran great after that. Now just a few months later it's happening again.

Anyone have ideas?

 

Yes, the Throttle Position Sensor. Try contact cleaner on the throttle position sensor plug.

 

Ok, just went out to garage to attempt that cleaning. I could not figure out how to un-attach the sensor wiring easily so I stopped. It appears there is a center clip. I tried depressing and pulling up on but neither made the wiring harness move, so I stopped.

BUT!!!! While there I did notice that the large silver hose clamp that is supposed the hold the air tube to the Throttle Body was not even tightened. Could it have vibrated so loose that it caused an air/vacuum leak in the air/fuel system? I tightened it back up but have not tried the engine again as it is getting late in the day and I am tired of it. Will try tomorrow.

 

Sounds like you stumbled on to the hardest thing to find, a air leak.
Good chance in that positions it could give all kinds of codes.

 

If it runs you should be able to watch the fuel trims via OBD and see if there's an air leak.

 

That might just be your problem right there.