Thought to write a short summary of my D3 V8 and the P0171 code or in longer form known as “P0171-00 (AA) System too lean (bank 1)” that I got the other day.

Having read a few of the horror threads on this in the past, some with no obvious conclusion or fix, I thought to try to resolve this by collecting some data.

As I have an IIDtool I was able to read some live values, among them the “target intake air flow” (requested) and “mass air flow” (actual supplied) values. While there wasn’t much variance, the supplied seemed to be constantly slightly higher than the requested.

Logically this should mean that there is either a leak in the air duct going from the air box to the throttle body… or a vacuum leak somewhere else.

For good measure I removed the MAF and sprayed it richly with CRC Air sensor cleaner. The guy in their YouTube video would be proud of me and the amount of cleaner that I used.

The throttle body had slightly black edges so I cleaned the throttle body duct itself from any residue using isopropanol and also the butterfly valve, also the sides of it.

I also replaced all the O rings on the following parts:

• PCV valve, two O rings, they were slightly deformed and did not return to their original shape. The PCV saucer itself was replaced in 2017 so 6 years is all it takes inside a hot engine bay….
• The O ring at both ends of the PCV Left Valve Cover To Intake hose (4584559)
• The O ring at both ends of the PCV Valve To Intake Manifold hose (LR005991)

After that I reset the codes and test drove about 200 km. To my relief the P0171 code and the CEL haven’t come back. The vehicle also feels much more responsive. Knock on wood and all that…

Hope this is useful for someone.

 

PCV valve did it for me as well. First part I would replace with this code in hindsight. I also got better acceleration and about 2mpg better mileage.

 

I did the o-rings on my crank case tubes a while back and had a hard time sourcing the proper size. Noticed a week ago I had oil around the PCV tube, it was soaking upwards. I put better o-rings on this week and that is when I noticed that the o-rings are not the same for both pipes. The crank to intake tube uses slightly smaller ones.

 

A friend happened to have an O ring kit with a gazillion different ones in metric sizes. It is fortunate that these were all in SI units rather than some obscure imperial sizes 😂

In my case the PCV saucer was nice and dry. As a part it is relatively cheap, however, and if it would fail creates very weird issues.

One of my pet peeves in the D3/LR3 is that it’s somehow a Frankenstein monster in terms of screws and bolts… some parts with numbers trace all the way to the Rover Corporation and it feels like the product managers specified and procurement bought parts in the early 1980s that they had stock of 15 years later and management made them spend all. Then ze Germans made them buy metric parts they also had surplus of and Ford Europe and Ford USA had their own thoughts about things, etc.

 

Glad folks are chasing down these old o rings. Another spot that's been troublesome for me is the oil filler neck and oil cap. Both have large o rings that shrink and are a breeze to swap, particularly the one at the bottom of the oil filler neck. It screws out just like the cap, sometimes unscrews a bit while removing the cap.

the colors on these o rings indicate the material they are made of, and they are picked by engineers to stand up to the fumes/fluids going through the relevant fitting. Be sure to replace green with green, black with black, etc so they hold up as long as the originals.

 

Indeed. I actually replaced the filler neck and cap with “new” a few years ago.. found an unused one somewhere cheaply.