My 2006 LR3 V8 4.4 is developing an issue that seems to be getting worse, hard to say. The ONLY codes I am getting are for both banks lean. No EVAP codes, EGR, etc. Issues involve stalling at stop signs and hard starts when cold. When warm it seems to start just fine.

What I have done is swapped 2 different MAF sensors around (so three in total). I have swapped in a used but good PCV valve. I have examined intake plastics for cracks, while there are some and I have sealed them in the past there are no new ones. Throttle body cleaned. EGR cleaned and verified default position was closed (not stuck open). So then I moved onto the vacuum system. I plugged the PCV valve at all ends (intake tube connection, both ends and I disconnected at intake). That stopped the PCV hiss so I could hear better, but also ruled it out as the issue. So then I pulled the purge hose - the one that attached to the throttle body at the upper back (points to back of engine) and plugged both ends. The only vacuum connection I have no tested is brake booster. Blew out my left knee, so hard to get behind the engine. Anyway, with every blocked up and an adaptations reset of the engine, there was no change. If I tapped the throttle to spike RPM it would not and if anything it would stumble a bit. Also I did try a propane leak test and starting fluid test. Starting fluid test was done with a cold engine and viscus fan held. Used a whole can all over the engine. Nothing. Also of note, no fuel smells around truck at all.

So at this point I am leaning to my new, eBay, fuel pump going out already. I still have the good factory unit which I thought was defective but it was instead a wiring issue. But running this past the forum to see if there are any other ideas I can do before dropping the darn tank again. I think I ruled out any emission hose leaks by blocking it up and I don't think its intake ducting - this would also rule out a leaking filler cap. Could be the intake itself, don't hear a leak tho. No recent work has been done to the truck.

EDIT: I will add that long term fuel trims can easily hit 15%. Short trim rarely exceeds 10, usually lower singles/negatives.

 

Have you checked fuel pressure to see where it's at?

 

Its a 2006, no fuel port on the rail. Really annoyed they removed that otherwise I certainly would have. I would have to somehow hack the lines. Although I have thought of making something since I have access to two wrecked LR3s. Maybe a pain, but I could maybe make an adapter that plugs into the output line forward the tank and next to the transmission.

 

Update: So this morning I tried something new, swapped fuel pump relay, reset adaptions and cycled the key a ton of time before doing a cold start. Would not start easily at all. It tried and tried but it was a huge struggle. I have an aux battery that I engaged, did not help. But that does give more juice and a secondary ground. Once she fires up though and gets through the initial struggle, it runs. I swapped the MAF yet again and yet again inspected intake duct plastics. No luck. And yet again I pulled various vacuum ports/hoses with no help.

So huge struggle to start even after numerous key cycles, slow throttle response to quick changes, stalling. Found the old fuel pump but I have a quarter tank to burn up before I try that hell again, even a quarter tank is no fun to lift. But I still want to see if I can produce a make-shift fuel gauge setup to test.

Video added. When I quickly "tap" the accelerator peddle you can hear a loud sorta hiss. I am not sure if this is normal, the throttle body or some yet unseen vacuum leak. I did this with the PCV hooked up and totally blocked up, same result.

 

Well crap, appears to be fuel pump if my 20 year old never used gauge is correct. The stalling is getting worse, so unless a vacuum leak can get worse over time (usually not) then I guess into the tank I go, again.... PSI of 35 is nowhere near the spec of 65psi. The handy fuel line interface I made worked well tho. Jumped fuel pump relay to ensure it would run for more than a couple seconds with key turn.

 

Well its not the fuel pump. Amazing how fast I can swap pumps now, 3 hours is nothing compared to the first time. Then again this time the pump would run so I could empty the tank. A light tank makes light work of this, thats for sure. Sadly the new pump has resulted in the same issues. I was excited cause it started to easily after the swap. But once I got down to the county road, it died. Then wanted to die in the round about. I pulled to the ramp shoulder and it died. But once started cruised at 75mph just fine if a little sluggish to throttle.

New discovery. When I go to sport and WOT it will hold gears for dear life after letting off the peddle.

And as for the gauge, well apparently its broke. The replacement pump ready a little over 40psi but when I starting packing the dial it climbed. So another reason the pump may have been fine as well as the now installed original.

Oh, same codes came back too. Both banks are reading lean. I can only circle back to it being a vacuum leak issue, one that would start out minor and get worse over a week. And I did check brake booster lines. They appear fine and when I disconnected the booster, after the engine was off for some time, there was plenty of remaining vacuum.

 

The fact that it struggled to start after resetting the adaptations bothers me. That really sounds like its a legit vacuum leak or fuel issue. When you did the checking for cracks - did you smoke it or just visually look for breaks?

 

Visual w/scope after removing throttle body. So since my last post I swapped all intake plastics before the throttle body and I swapped the throttle body itself. No change. So then I blanked the EGR with a thin piece of metal. Interestingly I have yet to generate any lean codes, just an EGR code. But behavior remains the same, stalls a lot especially coming off the highway. Round town its a bit of hit or miss on stalling and I generally cost to stop to prevent budding RPM fluctuations.

Would like to do a smoke test so I may DIY something. New fuel pressure gauge setup came so I will do another run on that.

Def agree, fuel or air issue and I keep flopping between either. At this point it has to be intake manifold or fuel pump wiring. There is no much left. Pressure test will hopefully yield good results. I have access to two spare intakes, so I can swap if needed.

 

So I checked pressure with the new gauge, 40psi..... I guess I can not rule out my "known good" pump being bad form sitting on a shelf, not in fuel to protect it. But this weekend I will drop the tank, AGAIN, and run independent wires to the connection on the tank. Like I did the first time I had pump issues and found out it really was wiring ( https://landroverforums.com/forum/lr...issues-105279/ ). I did inspect the wiring at the connectors behind the passenger wheel well liner, a known hot spot for rubbing. All looked fine. Pins inside connection looked clean. The ground for the fuel pump takes a different route, I think out the back end to the connectors behind the driver side rear airbag. I would think bad wiring would not create a low performance issue, more of a dead pump issue. Of note, voltage across fuel pump relay was 12.36.

So for now I will concentrate on fuel supply I guess. Possibly even an in-tank issue. Granted the fuel supply swap included a pressure regular swap and fuel hose to fuel tank hat swap - which would include a different o-ring on the end.

 

Another diagnostic update. Have not yet dropped tank on my truck. Yesterday I prepared anther tank from a wreck and also tested its pump with my gauge. 65psi. So I have a good tank/pump combo ready to swap for sure. But I also tested the eBay pump by placing the complete pump/pot housing in a container full of fuel. Pressure read 60psi. So this seems to likely rule out pump issues and point more towards wiring.

I actually have two theories. One is the swirl pot itself. When I first tested the pump I had no lower half of the pot installed and we noticed the upper filter just shot fluid straight out, no pressure. After looking at things, we saw the lower pot portion has a sorta output screen setup. This is where the top large filter's second output, which points down, was directed. Yet for pressure to build, this would have to be restrictive in some way since free flowing allows no pressure to build. I pulled the metal clip on the outside and nothing was obvious. But in theory, a failure there would me low/no fuel pump output. And I will add that when swapping pumps I did reuse the same bottom half since my original old one was dirty inside. So I currently have my original pump installed with the eBay lower half of the swirl pot. Thus a failure there would have been carried over and the result, same low pressure issue.

Second theory is the fuel tank hat itself being bad. I know there was an update, but I swear I ran across some old threads where people had these fail. Cant find those threads on any of the forums (my search parameters are probably wrong). Called a friend, he thinks he recalls reading the same thing. This is why today I will swap an entire tank setup over, wire it up and see what pressure I get. Low, wiring on truck. Good, then it was the tank cover (Rover Part # WGC500130 ) or is was something with that swirl pot lower output. Will know later today as I get ready to swap the tank.