I picked up my 03 XJR and drove it home yesterday (600+ miles). About half way, the CEL came on but there was no loss in performance or other issues. I had the codes scanned and got:

P0171
P0174
P1642
P1000

I've searched this group of numbers on this forum and found a couple of members think this grouping of codes indicates a vacuum leak.

What is the best way to begin a vacuum leak check?

 

go to the live mode on your code reader and check to see what the map measurement is. If it is zero, the leak is the map hose to the sensor, right at the rear of the engine, just forward of the firewall on a bracket. The hose comes off my car periodically. I hook it back up, and the light goes away in a few trips.

 

This might help http://www.gusglikas.com/AutoRepairTroubleShooting.htm

 

That's pretty good info. Now what did I do with that smoke machine?

I'm a decent DIYer, but I set up an appointment with Buckhead Imports anyway. Since I just bought the car it would be best to get the CEL issues resolved by pros so that I can get a tag for it.

Any help with P1000 or P1642?

 

Take a look at youtube.com to give you an idea Try this link http://www.youtube.com/watch?v=KMJac8t8JXU

 

Buckhead Imports got the car this morning and quickly diagnosed a bad vacuum hose underneath the manifold (most likely using their smoke machine). They're overnighting the parts and should be finished tomorrow. Expensive hose! Welcome to the Jaguar Kingdom where everyone pays!

 

Got the car back this morning and I'm happy to report that it's running great!

 

What vacuum hose is under the Manifold ? What had to come out?

This is the kind of part that will start to cause problems for many cars -- since they are all 8 years old at this point.

 

I was just told that the vacuum hose under the manifold was leaking causing the unsteady idle and the CEL to light. I know that the shop has a smoke machine and by the quick diagnosis (less than two hours), I'm sure they used it this time.

The job write up says:

renew trans valve body plug -
part number 203-540-02-53 - valve body conn.

renew evap purge vac hose -
part number AJ8-4879 - vac hose

What they had to remove I have no clue. I have had the car for less than a week and have not really had the time to get familiar with many components/parts.
For example, I have no idea what the "trans valve body plug" is. Can you tell me?