I have had a persisting issue with my 06 XJ8 (145k) for months that has recently gotten much worse. For a while now, the car will randomly have trouble cold starting. When this happens, the engine turns over but isn't getting enough fuel to idle.
This issue has been happening more frequently. A couple of weeks ago, it started to misfire as well and I have seen the "restricted performance" message appear while driving once.
I took the car to an auto part store and they ran codes P0174, P0171, P050B, and P0101.
I have since change my fuel filter and used a fuel additive in hopes of it being an easy fix, but no change.
I am not sure if the issue is with my injectors or my fuel pump, but I imagine that it is my pump given that both banks are misfiring due to being too lean.
How can I be sure what the issue is before I start buying parts? Where should I go from here?
Thank you in advance!

 

You will need to check fuel pressure to see if the fuel pump is the problem. I am not sure if there is anywhere on the fuel line in the engine area that a gauge can be attached. Hopefully someone else will have that info. I use a scan gauge that plugs into the diag port and gives me live data as I drive the car. I have the gauge set to watch coolant temp,fuel pressure and charging.So you may consider a scan gauge as a way to see fuel pressure.

 

The P0101 code might be your starting point.

MAF sensor circuit range/performance.

• Blocked air cleaner
• Air intake leak
• Engine breather leak
• Throttle control malfunction
• MAF Sensor to ECM sensing circuit: high resistance, intermittent short circuit to ground
• MAF Sensor supply circuit: high resistance
• MAF Sensor failure
• Throttle adaption fault (check throttle position voltage at Ignition ON)

 

Try a hard reset
https://www.jaguarforums.com/forum/x...esolved-96381/

 

Hi @JazzCatt , hopefully someone here can help you out. Do you have a diagnostic tool? If not you can get a cheap (for now) bluetooth OBD2 connector on Amazon and download one of the apps on your phone. I use Car Scanner, others prefer Torque. Anyway, you can read fuel trims and fuel pressure using these devices, which will help to diagnose the problem without throwing a bunch of parts at the car. Let us know what your fuel pressure and short term fuel trims are at idle and at ~2000 RPM.

 

The fuel rail should have a valve (I think it is called a "Schrader valve") on the fuel rail where you can connect a pressure gauge, at east my SV8 has one and it is located on the right hand side of the engine towards the back of the fuel rail.

You can see it in the following picture, I have circled it in red. On my car the valve has a blue cap.



I assume that also the n/a engines have this valve.

Best regards,

Thomas