I have been getting a PO171 code for several weeks. My 2005 Jaguar X-Type VDP will "cough" and "studder" when stepping down on the throttle when going about 50MPH like it's starving for fuel. We have done the following to address this.
New Plugs
New O2 Sensors
New MAF Sensor
New Coil Packs
Checked PCV Valve
Checked Vaccum Lines
Checked Catalytic Converter
and even replaced the Fuel Pump
None of this has remedied the issue. Any suggestions would be appreciated.

Thank you,
Dennis

 

Start with checking the air intake duct between MAF sensor and throttle body ....looking for any splits in the ribbing that are introducing additional air after the MAF sensor.

I assume you are not also getting any P0174 "Bank 2 Lean" codes as well. Nor are you getting any ignition coil related codes P03xx
If no P0174 codes, then it is just bank 1 reporting.
So you can probably initially set aside looking at shared sensor inputs (MAP, (IAT, MAF), ECT, EFT and IP sensors). Common fuel rail pressure and pump can be excluded for the time being too.
You might want to double check bank 1 O2 sensors and check for any exhaust leak on bank 1 before cat converter (an exhaust leak would be quite audible I would have thought).
You might have an injector or two that are under delivering on bank 1, so you might decide to just swap injectors from bank 1 to bank 2 for a test to see if fault transfers and your code then becomes P0174.

 

Yes, you are correct I am not receiving any other codes. I will try what you suggest and see if that works. Thank you.

 

What are the fuel trims (tested in the way so often posted)?

(For example, you may be close to P0174 as well and the above will show either way.)

 

I am sorry, I do not understand your question about "fuel trims".
EDIT: I do not believe my OBD reads fuel trims.

 

Plenty of posts to read & learn.

Cheap suitable tools are $5 or so.

 

Okay... thank you.

 

ELM327 and torque app for your phone.