Lean only codes were traded for evap only code by disconnecting the purge line.

In my case I did not have any evap codes.

 

Gotcha re purge valve.
I disconnected and reset the adaptation settings. But then! i got a parking brake fault which shut down the audio- hahaha! reset the car with a saved configuration. I will plug up the tube and see with the current configuration (w/radio).
Thanks!

 

Question


I have been talking with a few other mechanic friends this week about lean codes. A couple of them are suggesting the throttle position sensor. If I understand these engines a tiny bit… they do not have separate throttle position sensor. These are part of the throttle body. The entire throttle body must be replaced,

After multiple vacuum leak repairs. I am still getting bank 1&2 lean codes. After further review of the fuel trims too, I am starting to see that my LTFTs are high only in park as well at idle and at around 1500 RPM when in drive. I’m starting to think this might be less of a vacuum hose leak and more of an oxygen intrusion from the throttle body in the wrong position. Can anyone help confirm this theory before I spend any money on a used unit??

Also FYI, I tried the purge valve discount trick. Removing the purge valve hose from the throttle body and plugging the T.B. Inlet definitely corrected my lean codes. However, after only about 30 miles, I still got Bank 1&2 lean as well as the Evap Code. I determined that I have a leak in the purge valve somewhere but this is not the main issue.

 

Mine does a similar thing with the LTFT and idle or park.

Ordered the upper intake manifold gaskets from the local Land Rover dealer and they should be here next week since it's warehoused and and old VIN/part. Also ordered another set of lower intake manifold gaskets since I'll be un-torquing the manifold to remove it. The parts guy thought it'd be cheap insurance and to order it from BA as they have the better price. I don't want to do it a 4th time so figured he's right as insurance.

Will update when everything arrives and is reinstalled.

 

OK, here's my update...

I have not had any confirmed or pending lean codes on either bank since disconnecting my evap purge line (566 miles / 2+ weeks, daily driving), BUT I don't think the purge line really had anything to do with it.

My thought was that the purge was possibly impacting fuel delivery. After a week of driving with it disconnected, I did nothing more than reconnect it, and the codes did not come back as I thought they would. Sorry if I sent anyone on a wild goose chase with this, but at least it is easy enough to do and undo.

I did rig a schrader valve at the fuel rail so I could monitor fuel pressure. I ran for 4 days with a gauge at the windshield wiper watching for pressure blips at various states of acceleration. Spec. is 65 psi, and I consistently saw 65-67 psi. I am eliminating low fuel pressure as a participant in triggering lean codes.

Ultimately, I believe the new intake plastics brought my system back to just below the threshold of triggering lean codes. My LTFT's are still too high, roughly 8-13%. Both banks are tracking closely with no misfires in any cylinder, and no other codes, so I don't put much weight into a clogged injector as a cause. If they are all equally clogged...maybe.

I'm curious about the throttle body as Coldwater mentioned. This is a really good dig into a very similar style of throttle body: . The plastic gear slop looks like what I try to feather out of the throttle on initial takeoff. Seems like a long shot for lean codes unless the gasket is bad, and there's no good way to take it apart.

I think I'll need a smoke machine to dig any deeper on mine. Maybe a new MAF, but I hate to throw (expensive) parts at it without verifying.

Good luck to the others on here. I hope one of us has a breakthrough soon!

 

Update: January 21st, 2023 - Welcome to Today's Rollercoster
-------------------------------------
I bought 8 new genuine upper intake manifold gaskets from our local Land Rover dealer. They had the best price by far at $19 each rounding out to around $164 for all 8 which made me happy. Everyone else had them for over $20. I also bought two new genuine lower intake manifold gaskets from Atlantic British since the previous new ones were probably going to be shot when removing the manifold for the 3rd time to get to the uppers.

When pulling the fuel rail I sheered one of the Torx screws while loosening it with almost no force so I think it was cracked and ready to break so it did. This is what the universe calls a sign.

Luckily when the fuel rail came off I was able to use a set of channel locks to remove the screw without issue. Sourced a new stainless 10 x 3/4" course thread pan head screw at the local hardware store and it fit perfect.

Removed the old gaskets and took some comparative shots of the old tired ones I removed, the new genuine ones with the weird cube things for the older VIN numbers and the new style of gaskets for newer VIN numbers without the weird cub things. ​​​​​The difference between the worn ones being removed and the new replacements was incredible. As shown below, the old ones were ground down and severely pitted



LEFT: new style gaskets for newer VINS (doesn't fit mine)
MIDDLE: old gaskets
RIGHT: new green gasket with cube things for older VINS (that fits mine)
TOP: sheered screw



New gasket installed on the far left and the old ones still in. There is serious degradation of the old ones.



New gasket installed on the far left and the old ones still in. There is serious degradation of the old ones.


I removed the MAP sensor and cleaned the bejesus outta it until the spray dripping out was clear (it started out black).

So it all got cleaned up and put back together to find that 2 of the fuel rail Torx screw holes are stripped which may be one reason why I had lean codes and a lot of fuel or oil in the upper gaskets when the fuel rail came off. I'm guessing it had been loosening over time. I used some flex gasket goo on the screw to try and get a bit more grab on them which I was hoping was better than JB weld or some other adhesive that'll be a permanent bond and keep it from coming out ever again. The screws threaded nicely, with and without the goo, but I couldn't apply a lot of torque without them just spinning. Many colorful words were uttered at what could be universal sign number 2. This may come back to bite me but I see the only way to fix this particular sub-issue is a new intake manifold.

Reset fuel adaptations after everything was reinstalled and then it went further to hell.


First Drive
-------------------------------------
Went for an 8 mile drive which did not go well. Rough idle right out of the gate so I used the GAP tool to record some injector pulse waves looking to see if the flux in idle was due to an injector issue. Not that I have any idea what I'm looking at but I figured it should be obvious. Fun fact for the evening: the log did not capture the graph. It did allow me to dump a .csv file which I made into a PDF called Injector Pulse Width is someone is able and willing to translate that's attached.

I also captured long and short term fuel values, engine speed and MAF sensor readings in an attached PDF called First Drive.

Aside from the rough idle the truck felt heavy and unresponsive, almost like it was flooding the engine. It would go but was not happy.

The Big Fault
-------------------------------------
Eventually I got a flashing engine light while idling at a stop light and a quick information center advisory reading 'engine system fault'. More internal cussing and a half second of panic I turned the truck into a brick. But when you FAFO, you are gonna find out so I did what I do best and keep on keepin' on because I was 5 miles from home and it started to snow.

Odd thing though was that when I would accelerate or drive it would go away and be fine, other than not peppy. Did this twice but it was no issue when driving so I wonder if it was starving or drowning for/in fuel. So I did what anyone would do and captured another GAP tool reading which I've attached titled the Big Fault.

Then the computer finally decided to throw codes. All of the codes.
For cylinder misfire on 2, 7, 3, 4 and 5 plus the random misfire and misfire on startup for good measure.

A LOT more internal cussing ensued. Photo below.






Second Drive
-------------------------------------
So I got to the destination, turned off the truck for about 2 min. and then resumed driving home.

Immediately the truck was back to normal. Fully responsive, no engine faults, no crazy idle or misfiring and lots of giddy-up. Cool!

In keeping with tradition, I captured a log of the drive home which is attached titled Second Drive.

All was well until the LEAN CODES RETURNED. They returned ya'll.
As in they are F---k'in back. Are you kidding me? Really?


Final Thoughts
-------------------------------------
Is it the screws without a lotta bite? Is it something else? I will smoke test it tomorrow and try not to loose my cool.

I'll leave this here in hopes someone has some idea of what to do next because I really have no clue.

 

I don’t see an attachment for 2nd drive. On both your first drive and big fault, the short and long fuel trims aren’t anywhere near triggering lean codes. All 4 look to be stuck at around 1%. I suspect you never reached closed loop fuel status on either drive.

To trigger lean, you need STFT in the +20% range for more than a few seconds. I’m not sure the exact trigger, and it doesn’t matter. If FT stays high, you’ll get your lean codes.

 

Oops - I've attached it for real here.

 

Well, I’m not a Fuel Trim analysis expert, but I can see where yours are running high enough to trigger lean.

It looks like the worst is when you’re out of the throttle, which I believe still points towards vacuum leaks because the leak is a much greater percentage of the total air running through the motor to keep it idling.

I’ve read exhaust leaks can cause this too, but I would think that would be 1 bank or the other, not both. But I just guessing here.

I wish I could be more help. I just don’t know. Mine is much the same, but for now, it’s holding below Check Engine Light triggers.

 

I’ll smoke test it today I hope.

I was thinking with both banks triggering it’s not the stripped screw holes because that’s only one side of the upper manifold. 🤷🏻‍♂️