Hello everybody:

My 2004 Jaguar XJ8 has the Check engine light on and also the Restricted performance and OBD codes read P0171,P0174 too lean both banks 1 and 2 .

I replaced the MAF sensor with an OEM Denso part #
C2S2670 and still have the codes. It has 258,000 and
I think still has the oxygen sensors from factory never
changed them . I bought the car with 52, 000 miles
and now it has 258,200 .

car drives find , spark plugs are new, also the fuel filter,
I don’t know about the fuel injectors or fuel pump but when I floor it sometimes it stalls only if I suddenly floor it to go faster.

Any advise ? Or I can just simply replace the upstream and downstream oxygen sensors , eBay has a deal going on of the Denso oxygen sensors for $365 OEM.

Any suggestions of how to proceed?

Thanks

 

I would check for an air leak in the intake between the the filter and throttle body, A crack or a loose clamp perhaps?

 

Thank you

 

What do the fuel trims show?

BTW there a LOT of threads about what to measure & when etc.

 

Good chance if it is not any of the basic plastic intake piping & smoke test shows nothing.
Those eight pesky hidden intake manifold gaskets are what your looking for.
As for the oxygen sensors, many consider them a wear item, much like spark plugs.
Use the stock oxygen sensors, which i believe are Denso's.

 

Watch my video ,, I found a vacuum leak , it is a broken hose that comes out from the back of the throttle body and goes to the base of a connector on the injector rail .

I need the name of that part , any idea?

 

The vacuum leak was a broken thin hose that comes from the back of the throttle body and connects to the Fuel injection pressure regulator sensor.

the hose broke at the base where it connects to the sensor located on the fuel injectors rail.

 

 

I got it from Barrett

The vacuum leak was a broken thin hose that comes from the back of the throttle body and connects to the Fuel injection pressure regulator sensor. And a Vacuum elbow that attaches to the sensor.

The hose broke at the base where it connects to the sensor located on the fuel injectors rail.

 

Nice find!

Are the trims now OK?

 

I do not know but The check engine went away. I am wondering if I should replace the oxygen sensors since they never have been replaced.
My jag has 258,200 miles on it.
2004 Jaguar XJ8

 

I chased a lean condition with no vac leaks forever, when it ended up to be O2 sensors. Fixed my problems and brought my trims back to normal. Check the voltage on them with a live data scanner prior.