I'm collecting bottles and cans to get more $ to try to get this fixed:<)

All of the O2 sensors have be changed...twice. Yup, I've gone through 2 pair of front and back O2 sensors. The first thing anyone who works on it suggests is replacing the O2 sensors. Then they find out that the sensors keep the SES light off for about 25 miles and then it comes back on with the same codes.

My most recent diagnosis (1 month ago) was from a moonlighting dealer mechanic. He says the cats are clogged. He suggested I junk the vehicle because he has always had bad results when trying to replace cats and the high mileage on my vehicle. Being of the baby-boomer generation, I've got a few miles on me too. I hope they don't want to junk me!
I had a necessary valve job 2 months ago that I hoped would have an effect on the problem, but it did not. In hindsight, I kinda wish I had the engine replaced instead. Maybe that would have corrected the problem.
Anyway, I am where I am and would like to save my beloved D2. The MAF suggestion is the first that I've heard from any of the mechanics. The most difficult part of the entire process if finding a local mechanic that is affordable, knowledgeable, and gives a darn. I'm open to suggestions and will use your suggestions as best I can to resolve the problem.
My belief, "By definition, every problem has a solution."

 

I wonder if the issue is the wires or the ecu.

 

98% of all O2 codes on these trucks is because of the need of a tune up.
I did not mention it before because I ASSumed the shop did that when they did the valve job.
When the spark plugs/wires go bad they spark gets weak and does not combust the fuel completely sending to much raw fuel downstream, the O2's then read out of range and throw a O2 code.
Anyone who does not know better is going to replace the O2's because thats what the code is for, which makes sense, unless you know better.
This is missed by everyone, including LR techs at times.
Have the plugs and wires replaced, use whatever plugs you want, spend the money on the wires.
If your budget is $100, spend $80 on wires and the rest on beer and spark plugs, in that order too.
That would also make sense as to why the CEL comes back on so quickly and your rear O2's throwing codes because the cats are running to hot burning up the raw fuel.
And yes you can replace the cats on a high mile car with no problems.
I bet he would have taken the truck off of your hands for you if you would have agreed with him.

 

You must know the guy. Isn't that really sweet and considerate of him to want to take it off of my hands

I did have one mechanic who is not Land Rover specific suggest a new computer. I'm really between a rock and gas pump. It costs as least $92 for a gasoline fill up. And I need to fill up AT LEAST once a week. I'd love to drown my sorrows in a few brewskys, but the gas prices are killing me!

What this really boils down to coming across somebody who treats people like I do. I'm a telecom engineer. When someone comes to me with a problem, they describe the problem and I give them the price to repair the problem. I usually resolve the problem quickly and collect payment. If it takes me more time, or if I did not do the research that I should have to fully understand the problem, I don't go back to the client and ask for more money. I fix the problem and collect the agreed upon amount. EVERYONE WHO I HAVE TAKEN THE CAR TO HAS PROMISED, BUT NO ONE HAS DELIVERED! It's now spring and turkey season is right around the corner. I'd like to get this fixed so that it doesn't cost me $184 (2 tanks of gas) to miss a gobbler

Is my only option to replace the O2 sensors, MAF, ECU, plugs, wires, and Cats? Or, will a quality mechanic be able to pinpoint the problem and stand behind his diagnosis? Thanks guys.

 

its paying attention to the vehicle thats important. for example the oxygen sensor codes you have to do some diag. If you are putting the right ones in and nothing is damaged then you have to do some wiring tests on the sensors. Personally I would test all the sensors, disconnect the pins at the ecu and check to see that they actually change resistance as it heats up. if it doesn 't or goes haywire then you are looking at an issue with wiring or the ecu itself. You have to sink your teeth into a repair like this. I have done repairs like this and yes it takes a lot of time but its not so much time as it is paying attention to what is going on. Even a non land rover technician worth his spit could diag this repair with the right information. It just costs money to do something like this. But you can do the same yourself if you learn how to diagnose a vehicle.

 

The fact that the O2 sensors on both banks are calling foul tells me to look for either a vacuum leak, an air leak after the MAF (check the air intake tube for breaks or cracks, the idle valve hoses and clamps for the same), or the MAF itself needs to be cleaned or is faulty.

If you haven't done a tune up in a while, now's a good time. You don't need to get the most expensive wires on the market either contrary to the gospel of some folks. A middle of the road set of NGK wires and NGK platinum plugs will do fine. I have NGK's and my truck is code free.

Start with these things, and then go from there.

 

The most encouraging part of everyone's comments is that this can be fixed.

To Roviin4Life -- I plan to use all of the tools and info provided here to help diagnose the problem when I find the professional who will take the time and PAY ATTENTION to what the vehicles needs. My biggest asset is knowing what I don't know and listening to somebody who knows more than me.

Just 2 brief examples of how the mechanics have not been paying attention:
- Late 2012 took D2 to small shop for valve job. When I inspect the block, I find 2 new valves and the others are the originals with carbon deposits. I request all new valves because...with over 300k miles, if 2 went bad, then all WILL go bad sooner than later.
- Early 2013 took D2 to moonlighting LR mechanic. I told him in addition to the SES, O2 sensors and poor fuel economy, the windshield washer motor (and some other electrical function) was no longer working after the independent shop (mentioned above) completed the valve job. He is the aforementioned mechanic? who said that he always had problems when replacing cats. His diagnosis was the wiper motor died and with all of the problems plaguing my D2 I'd be better off scrapping it. I've never had any wiper motor issues so I investigated further and found there to be a fuse under the hood next to the fire wall that was bad. Replaced the 23 cent fuse and all is well. So I don't have much confidence in anything he says.

I don't have the knowledge or tools to become a D2 professional, but I can do whatever it takes to find folks to keep it running the way it was originally engineered. Some of the frilly stuff put on the D2 to make it appeal to the urban driver can be annoying and sometimes dangerous. I got a blowout deep in the National Forest and found:
1. My hydraulic jack leaked and had no fluid.
2. The "cutesy" covers on the lug nuts were rounded off.
So, I put the jack under the frame and dug under the tire to be changed to get the wheel off of the ground. Then I used my Leatherman to peel the "cutesy" covers off of the lug nuts so the wrench would fit.

My D2 has too many adventures left in it to have this Smog issue send it to the scrap heap. Thanks for helping me find the answers.

 

 

Hill-ar-ious!!!

 

Those are not curtisy covers, those are part of the lug nut.
It is common for them to get rounded over like that, they trick is to use a hammer to pound the lug wrench onto the lug nuts and form them back into shape.