I have the dreaded PO171, PO174 codes on my 2004 XJ8 VDP, indicating engine running lean on both banks! I have read most of the threads here and on the internet regarding a vacum leak.
I cannot find a video or actual instructions on how to clean the MAF or the MAF sensor as one of the likely problems.
So, What particluar MAF sensor cleaner do I need to purchase?
Do I just spray inside the MAF and hope for the best? do I clean it out with a cloth? do I just squirt the cleaner all over the sensor?
Any help, directions, video, FAQ's , Youtube links will be greatly appreciated.....Many thanks, David...I appreciate that this may just be the beginning of my journey!!!!!

 

Not likely the MAF anyway. More likely you'd have rich codes.

Likely an air/vacuum leak.

 

Classic codes for an air leak

 

Injectors might have perished o rings. I had the same on one bank, discovered air leak in number 3 injector by poking around with a mechanics stethoscope and listening for the leak. Weeks of trial and error were solved in literally 2 minutes and some spare change for the stethoscope. I now swear by this "old school" method... Might be a good place to start. Check all vacuum lines and the VVT sensors too.

 

Thank goodness!! I found a vacum line was broken!!, fixed it, drove it for 10miles no restricted performance error!! Hope that was the problem....Thank you for all your input, Vacum Leak looks like the problem is solved...

 

djpxk8, I am happy for you! I have had the relentless p071, p0174 since I bought my xj portfolio. I have not been able to find the source of my codes. Hoping, praying, and looking forward to a resolution soon! It is a pesky little thing!
Chemosabe in NOLA.

 

WHICH vacuum line, and WHERE broken?

Some of us have Jaguars that are.... eerily similar... one might think the buggers had even been mass-produced to the same design... from common parts, even... but the Brits just don't DOOO that sort of "boring" thing....... do they?

 

There aren't that many vacuum lines on these! Lift the plastic trim cover, you will find a double nipple on the back of the throttle body. On lie goes to the fuel pressure sensor on the front of the right-hand fuel rail, and the other goes to a vacuum reservoir behind the right front wheel. That's it! (Other than the brake booster, but if THAT leaked, you'd know!)

Those line get extremely brittle with age, and both were broken on my car. I actually got the P0171 and P0174 after repairing the vacuum lines! My ECU had "adapted" to the fuel readings from the pressure sensor not having vacuum on one side, and when it did, its learned map suddenly thought the pressure was high, reduced fuel flow, which gave a lean condition at the O2 sensors. I'd clear the code, it would come back after a while, but took longer and longer to come back, eventually never showed again. Kind of weird getting System too lean after fixing the vacuum leak, but after a while, and thinking it through about the pressure sensor going higher than it had been without vacuum on one side, I realized I just needed to let the ECU re-learn its map. Eventually the MAF, fuel pressure, and O2 circled around each other and converged on a new correct fuel map.

The line to the fuel pressure sensor was an easy fix, just some hose and a couple of couplers, but the other line was an entire assembly that I only found on eBay, not existing at any dealers I could find. That's the Secondary Air Injection Vacuum hose, part # C2C22716

 

djpxk8, good for you fixing the issue.
I fixed the same problem over the weekend. It was the breather hose. It was broken on the bottom and there was no hissing noise, so it wasn't easy to detect until I did the smoke test. The picture shows the brake as obvious, but that's only after I took out the hose and bent it a bit.

 

The rubber vacuum line had split where it joins the metal insert. Now cut off end and rejoined, everything seems ok so far!!

 

Great picture thank you!

 

Great picture, thank you!

 

The rubber vacuum line had split where it joins the metal insert

Just cut a new end for the vacuum line and refitted into the metal insert...Job done I hope!!