Yesterday I drove out a hour to a friends house. On our return trip home, I started the car and the engine started to shake and run rough. After 10 minutes of driving it would start running normally then back to rough. Error message eventually came up with yellow light - “Restricted Performance.” Curses and profanities ensued. I made it home and parked.

This morning I pulled the following codes:
P0174 (too lean)
P0300 (cylinders misfire)
P1316
and the regular P1000

I’ve also attached a video so you can hear it.


Thoughts?

 

You'll want to review this... https://www.jaguarforums.com/forum/x...cement-195018/

When's the last you changed the plugs?
Sounds like you have an exhaust leak or bad plug and cylinder not firing.

 

Probably not the issue but when I heard the engine the question came to mind "have the tensioners been sorted out?".

I looked at some of your other threads and didn't see a mention of the tensioners; if there was I missed it. I guess a timing slip could cause the misfire but again, that's probably not the issue here. On these cars though, it's always worth asking.

I bought a cheap smoke tester off eBay a few years ago and it paid for itself pretty fast. If you have a lean code and random misfires then a simple vacuum leak could be the problem. The un-burned fuel could explain the P1316. I found that the O-ring on the throttle body adapter where the brake booster line connects was leaking on mine. I spent a few dollars on parts and no more vacuum leak.

 

I agree with a vacuum leak as the likely culprit. I don’t know about the XJ8, but the XJR’s have a vacuum line that runs from the front of the left side valve cover area, under the intake, back to the throttle body elbow. The line is made of the world’s most brittle plastic and will disintegrate in your hand if you touch it. A smoker is best but you can try spraying some starting fluid around the front left area of the valve cover, under the intake if you can. If the engine rpm’s change, you found the leak. If the rpm’s don’t change, I’d still smoke it because I still think you have a vacuum leak. My $.02 anyway.