That post is pretty interesting! I've googled this thing til my fingers bled but never came across that - so I appreciate you posting that up. I have to wonder if that isn't the issue. Because I can't find any leaks in this thing anywhere....And I know the carbon buildup on mine is just as bad.

The more I think about your post the more sense it makes. If the injectors are spraying onto the valves and there is a lot of carbon on there, that fuel is being absorbed onto the valves in the carbon buildup while the air is passing directly into the cylinder. The computer is richening it up to compensate and viola...I can totally see it. It, of course, may not be it - but damn it sure makes sense.

I really appreciate you posting that up vetalbig. I assume there wasn't any change after the new gaskets?

 

I will be damned that is interesting

 

So here's my New Year's Update.

After reading VetalBig's post about the intake valves, I went ahead and decided to pull the intake manifold and take a look. I ordered new gaskets and they came in just before the holiday. So yesterday I got to tearing in. Overall, the process of intake manifold removal was pretty straightforward - the vacuum plug and electrical connector behind the manifold were a bit of a pain, but beyond that - a pretty simple process.

After removal my intakes looked about identical to vetalbig's. If you look closely at his shots of the intake valleys, you'll see the black sludge stop and turn into bare aluminum. This is where the injector spray obviously makes contact and washes the walls. Above that and into the manifold itself, its a sludgy mess of condensed oil vapor from the PCV. But my valves looked PRISTINE (at least on the intake side). I cleaned up some of the sludge that would come off - but I don't think buildup on the valves, or direct area, is the issue. I may still decide to do the motorvac as suggested by that post that vetalbig posted but that remains to be seen. I cleared the codes last night and need to get it out one more time to see if they have reset but I tend to think they will because unless there was a leak that was there that I somehow corrected (unlikely) then I believe the code will return.

So, still stumped pretty sure....

 

Shot in the dark... check the EGR return pipe connection at the back of the engine. The pipe connects to the EGR at the front and runs under the fuel rails to the back. The rear connection is impossible to view, but I drag my spouse out to tap on the pipe with a wrench so I can feel for the pipe about a foot down behind the engine (when cool obviously) on the same side as the EGR valve. We call this the disco reach around, lol. Mine works its way loose about once a year and kicks out lean codes on just one bank. A quarter turn (15mm spanner I believe) or so has fixed this twice.

Also, if you have a capable tool, reset your engine adaptation values after each attempted fix. My 06 LR3's algorithm memorizes the lean error state for about a week after the fix if I don't reset with a GAP IID to clear it out.

 

Thanks for that input! I actually wondered about that EGR pipe so it's worth a look. The sad thing is that I should have done it when I had the intake manifold off...that would have made it so much easier but I'll deal with it and see what I find.

Much appreciated!

 

Over the course of last week I sea foamed the heck out of my intake hoping to clear some of that gunk. Funny enough i ended up with both rich and lean codes for bank 1. Rich code went away after clearing it but P2096 stayed. Another thing I tried out of curiosity was unplugging rear o2 sensor. that of course cleared p2096 but caused open circuit code for that sensor. I tested voltage to front and rear O2s, that looked good. i will try tightening EGR pipe as well, thanks for mentioning that.

 

Found a pic of the egr pipe to help you guys out. It's #5 on this diagram. I also applied gasket maker to both sides of #3 and #4 cause I don't trust those flimsy metal gaskets alone.