2010 Jaguar XF 5.0 PVC Vacuum Leak

P0171 & P0174

I recently experienced a check engine light.  So off to the garage to check the codes.  Pulled the codes and found P0171 & P0174.  Oh Joy! 

Looked under the hood and did not see anything out if the ordinary.  Put the code reader back on to check the fuel trims and yes the short and long term trims were way off so I began digging deeper.  I had a half can of Throttle Body Cleaner and Brake Dust Cleaner and started spraying and watching my short and long term trims.  At first I thought I found it on the vacuum line connector in the back of the right hand cam cover but further checking it was found at the PVC valve.  They are close together.

This vacuum line is hidden from view but it goes to the brake booster.  In order to see it you will need to remove the cover located under the hood in the back at the window shroud to the brake fluid fill cap.  From what I have read this is one spot that has a common vacuum leak.

These two caps are your PVC valves.  My first attempt lead me to the vacuum line behind them mounted to the back of the cam cover.  After a little dialog with a Jaguar friend I did a little more checking to pinpoint the problem and found the leak on the aft PVC valve cover.  I mentioned that I used Throttle Body Cleaner and Brake Dust Cleaner while watching my fuel trims.  That procedure worked well and made the search so much easier.

After finding the leak I also realized that I could not remove the cover without damaging it so I ordered the new PVC valves first and had them in hand ready to install.  After further discussion I found the covers are a onetime use.  The best way to remove the cover was to use a pick to lift the cap stays to get the cap off.  In the process of doing that they just snapped off and the cap was no longer reusable.

This is the PVC membrane under the cap and under it is a spring.  I wondered how difficult it was going to be reinstalling the new one.

Photo of the membrane removed.

Now that I had removed both of them I wanted to find the failed membrane and it was aft of the engine.

This is one of the PCV caps.  As you can see I broke two of the cap stays and one was pulled back . Then I was able to remove the cap.


These are the two PCV valves that were removed and the pick used to remove them.

Before installing the new PCV valves I cleaned the inside and the channel that they seat in.

This photo shows the aft valve installed and the spring installed on the second one.

Like the first install I carefully installed the second one so the spring is lined up correctly.  At the same time I made sure the cap stays were lined up correctly for the cap to snap in place.

Both PCV valves installed and my P0171 & P0174 were cleared and all was good with the install.

However, I needed to reset the cars fuel trims and to do that I had to disconnect the battery.  I removed the ground cable at the battery and left it off for 15min then reinstalled.  Because of that I had to reset the emergency brake and reprogram the window operation on the car.




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