Yep - the OP got hijacked and others jumped in and muddied the water. That's cool because we are all in this together but makes it much harder to track.

Since I'm the OP, I'll provide an update. Replaced the fuel cap and PCV valve, MAF, a hose from the intake boot to the drivers side of the engine and then changed out the air resonator to an RRS one. CEL remains.

Ordered the intake reseal kit from Atlantic British and got all but the lower intake manifold gaskets since those are on backorder. Decided to hold off until all the parts are here before starting.

 

lol this is definitely a hot topic. I did do a smoke test with a home made smoker. Probably not very good one either. Results were inconclusive.

little update. My PCV and MAF are new and from Land Rover. I got to thinking today. My MAF might be new but I’ll try and give it a cleaning anyway. I took the MAF out and noticed that it has a very loose seal into the resonator. Which is also new. I cleaned the MAF then took some electrical tape and taped three time’s around the MAF O-ring. I shoved that sensor back in its hole… started the engine and I was amazed to see the CEL was off on its own. I cleared the codes with my GAP. Later in the day the CEL returns. Now this time it’s only showing P0171. Bank 1 lean. This is good news for me. I can now narrow it down. Bank 1 should be the passenger side with the PCV. I’m going to use my automotive stethoscope to try and find the leak now.

Results TBD.

 

I have regrettably joined this Lean Code Club!

Brand new to me 2006 4.4L, 164k miles. On the first day of ownership, I removed the air duct/resonator assembly to more closely inspect my water pump. I reinstalled everything, and two drive cycles later I had bank 1&2 lean codes. I removed the ducting again, carefully inspected for cracks, reinstalled, reset adaptations, and lean codes still came back.

I then began monitoring fuel trims.
At idle, ST and LT both good (around 0, +/- 5 ish.)
Reving the motor in Park, about the same.
Driving, under load (1/4 to 1/2 throttle), LTFT banks 1&2 both rise to about 15% then lower as load is gone and rise again under load. Increasing the load by manually moving to a higher gear and more throttle increases the LT fuel trims to 18-22 ish %.

Since I had thoroughly inspected my intake ducting, I began thinking of a weak fuel pump scenario—under load. But, if I mash the throttle, it goes??? I began looking into how I would check fuel pressure, while driving. Manual says there's a schrader valve, but there isn't (2006+). I read through Dakota's quest to conquer a fuel pressure problem here: LR3 Lean codes, both banks - need advice - Land Rover Forums - Land Rover Enthusiast Forum. Started thinking about making a similar fuel gauge adapter as Dakota.

Then I read this Lean Code thread where, after significant parts replacements, Dakota's speculation of the resonator plastic cracking was ultimately the solution: Back - Again :/ Still struggling to diagnose these Lean Codes - Land Rover Forums - Land Rover Enthusiast Forum. The OP, mirepoixmatt, posted a helpful video of his fix.

So, I went to re-re-inspect my intake. While pulling apart the pieces, the plastic flange on the resonator snapped, in the exact same spot as mirepoixmatt's. So I ordered a new PHD500025 Air Duct, and went ahead and ordered an air box too since most of the filter cover screw holes are stripped, PHB000476.

I'll report results ASAP.

 

OK, I have results.

First, I could not successfully seal the air duct, but I did find a somewhat reliable, undignified way to test it.



Leak test setup.

I duct taped the inlet, placed a large vacuum cap over the vent tube, then stuck my face into the throttle body hole and blew out my mouth. This makes a nice seal and you can easily feel and hear a leak. You can also feel/hear a suction leak.

I tried sealing the resonator flange with epoxy, hot glue, and silicone. They all failed the suck/blow test. So I machined a resonator delete fitting.




I though for sure this would fix it while awaiting delivery of the new air intake parts, but the fuel trims remained high under load and the lean codes came back.

With my air inlet confirmed sealed, I looked again towards the MAF sensor. I found this guy’s video and learned that I don’t know how to clean a MAF.


I was only cleaning the temperature bulb thinking I was doing it right. I used my scope to see inside and confirm it was dirty. Re-cleaned, properly, reinstalled, reset adaptations, and went for a drive.



Before


After cleaning

After several drive cycles and about 30 miles, in town and highway, no pending or confirmed lean codes.

By monitoring long and short fuel trims while test driving, I could quickly see the impact of my efforts. Properly cleaning the MAF made the biggest decrease in fuel trims. LT, under load is running right around 10, a little higher than I would expect, but the swings are not going high enough to trigger the CEL anymore.

 

Those MAF photos should be in a textbook!

So LT trim still at 10%. Seems like there is probably another small vacuum leak somewhere. There are some neat tutorials on making your own smoke machine if you want to go that route.

 

Yes, I believe your right, and I know I won't be completely satisfied until my fuel trims are more contained. I'm going to try and postpone further troubleshooting until the new air duct parts arrive. The nice thing is that I am able to learn a lot more about fuel trims by monitoring live values each time I change something. My journey from ignorance to understanding is long and ongoing!

This is a good MAF case study.

 

I’m making progress on my P0171 and P0174 codes. Ever since I taped the O-rings on the MAF sensor my 174 code has not shown up. I’ve now narrowed it to the 171 code. Check out this video I upload. Link below. I used come Carb and Choke cleaner and monitored the RPMs. It becomes very noticeable where the leak is located.

I need help figuring out what is leaking. I think it’s the induction elbow steal that connects to intake manifold. Can I get some input?

 

All this is great information- I just had my injector O-Rings/gaskets replaced and had a noticeable increase in "gitty-up" was able to make it about 75 miles before the codes popped back up. Next step for me is to take a look at where the EGR valve connects to the exhaust under the engine. Someone, I forget who, stated that this attachment point would not show up on a smoke test (due to location) and may need to be replaced/resealed. As for now, the warm amber glow of the Check Engine light beacons at me from the dash.....

 

Thursday I venture into the engine to remove and reseal the entire intake manifold. Anyone have any advice or things to be aware of while doing so? How to manage the fuel dump from the fuel rail, etc?

My shop manual and the one I can find online don't have the directions in it for some reason.

Thanks!

 

The fuel dump was not significant. A shop rag or two was enough to collect the fuel from the rail and hose. The correct tool to remove this fuel line is important too. Quick and easy removal. I would recommend removing the entire intake with injectors attached. Then pull the injectors off if you plan to get them cleaned and serviced.

I had a hard time pulling the coolant hoses from the throttle body. One ripped and I had to replace it. I did a full clean of everything and replaced all the gaskets from the Atlantic British kit. I used a little bit of clean oil when applying the new rubber gaskets, but I recently read that using dielectric grease is much better for the intake manifold gaskets at creating a better seal.

When I was tightening the throttle body back to the manifold I think I over tightened a screw or two on the bottom, which caused the threading to loosen in the plastic intake. Spec is 7ftlbs I believe. I tightened to 7 but had issues when tightening and now I’ve got a vacuum leak there.

Removing the intake and cleaning took me about 4 hours. Reassembly took about 45 min. I also replaced a couple vacuum hoses. I wish I would have replaced the thermostat housing while I had this all removed. My intake also has some super stupid green manifold gaskets that are specific to early UK models imported to be the US. I was in a bind and had to buy these from the dealer at ~$34 each. You can get these from British Parts of Utah for around ~$15 each I believe. My plastic parts, wires and plugs were also very brittle. The sensor at the rear of the intake was a pain to remove and is expensive to replace.

unfortunately all this work and I’m still getting a P0171 code. I’m so frustrated and exhausted from this issue.

This video here is a great look at removal of the intake.