I have 2006 XKR When i excelerate hard it surging, backfires,and power lose.
Installed new NGK Ir plugs, checked for vacuum leaks.
fuel pressure stays around 54psi. only code is P0171.

all works fine with slow acceleration

Also when I bought the car lat week both seat modules are missing
Dealer says the part # LJE2160AB Discontinued. I cant find them anywhere

also 30,000 miles on the car

 

Screen Shot of my scanner

 

Need to find out if your second fuel pump is working. Fuel pressure is falling. I know your car has low mileage, but check the underside of the bellows on your intake for any possible leaks.

 

I thought they went with only one fuel pump on 2005 and 2006

 

I was reading another post on here about 4.2 engines and how they changed the fuel delivery systems. it said some times the fuel pressure transducer can go bad. So I walked out to the garage and figured I would pull mine off and clean it. I was not thinking about the fuel pressure on the line so of course fuel went every where. But not long. as I just stared at it I noticed its just blowing air. I let it finish and put the sensor back on and it seems to be working fine now. No more stumbling or exhaust popping noises. I have not driven it yet.
Could it have just been air in the fuel rail?

 

Almost sounds like vapor lock. Is the fuel old?
Re the seat modules, there is guy that recycles Jaguar modules on eBay.
I bought a good used rear light module from him recently. Try a search on eBay, if all else failed send me a PM and I'll track him down for you.
Regards,

 

This sounds similar to a problem I'm having with a 2003, minus the pops and no backfire. It seems the car sort of falls on its face just slightly, when taking off from a full stop. I always thought there might be a transmission vacuum or electronic part to investigate, but had not considered the fuel delivery aspect. There's never any problems once the car gets going though - that's the odd part.

 

When I bought the car recently The last tags on it were from 2011. so Im sure it did have old gas in it.


Bought the car to fix and sell it but im realy starting to like it.