I am baffled (land rover content)

My Disco has been in the shop for a couple of weeks due to both an emissions problem not getting fixed and waiting on parts.

Long story short, right before inspection time the CEL came on telling me that the injectors were maxed out and I was getting some misfires. This seemed to indicate that I had an air leak and I did not have time to pull the intake myself to check it. The shop fixed a lot of little stuff, including one injector that only had one o-ring instead of two. With everything buttoned up, new LR O2 sensors, and a fixed exhaust leak, the computer is still throwing a CEL because the engine is "unbalanced" with one bank showing lean and one seeming to be running rich. As the whole engine runs through a single MAF and TB, I am beginning to wonder if the O2 sensors might have been damaged in shipping or installation?

Any other ideas?

A misfire on one bank, a leaky or weak injector, an exhaust leak upstream of the sensor, an out of range oxygen sensor, a serious vacuum leak at one port, although thats not really likely on a port injected engine, a badly designed purge system that feeds more into one bank than the other, and so on.  

Since you can take data, how bad is the imballance?

Swap O2 sensors side-to-side and see if the problem follows?

Can you swap the O2 sensors?

I was thinking about the sensor swap. I will relay that to the shop as they are just as baffled.

As for leaks, they smoke tested the entire intake, finding a couple of small ones and a few large ones around the injectors. I did have an exhaust leak that I didn't know was there., that has been fixed.

I will have to ask about how bad the imbalance is.

Thought of one more.  Is it possible to plug the left sensor into the right harness, and vice versa?  Thats generally a Ford problem, but I'm sure the Britmans could come up with a way.

Is it in the years that have the liner slipping problem?  

I would do a compression test and a leak down text. I know I know but it eliminates a whole bunch of things. 

I’ve had bad (CHEAP) O2 sensors out of the box. Did they for sure use LR’s?

What model disco are we talking about here? Which engine?

Disco2 with the 4.6. Supposedly with a new engine a couple of years ago (I may or may not have been scammed by the shop that did the work)

Have to agree with Dean, bite the bullet and do compression and leak down tests, get it out of the way. Wost case you find something bad and saved a bunch of time doing so, otherwise you'll know that the engine is mechanically right and you're chasing an ancillary related problem.

Did you have any luck clearing up the engine numbers as to wether they'd swapped out your engine or not?

Never heard back from Atlantic British on the numbers.. but the shop did discover the issue with the emissions. It was the Aftermarket MAF I put in two years ago. They dropped in a genuine one from LR and cleared the codes and none of them have come back. It defies logic as far as I am concerned, as it is a single MAF feeding both banks, but it did. I get to pick her up when my work schedule overlaps their open time. Probably monday.

Great news that the problem has been fixed, no matter how bizarre the cause. 

Is owning a disco worth it? I'm actually seriously considering buying one.... I just get the "unreliable land Rover" heebie-jeebies about going through with it.

It depends on what you mean by "worth it". Rovers are the ultimate go anywhere vehicle, but it come with two price tags. Most electronic repair parts need to come from LR itself or the truck won't like it, and you need to do a lot of maintenance.

The biggest problem with Discos with the 4.6 engine is that they are time bombs. It's a matter of "when" not "if" a liner slips and ruins the engine. The LR3 and 4 are much better vehicles due to their more reliable engines.

Once you get past the engine though, they are a fairly easy vehicle to work on, most everything is designed to be rebuilt in the field. They are rugged and can go most anywhere right out of the box. If I am honest though, a Toyota Land Cruiser is a better overall vehicle. I still would not get rid of mine. Between the time I replaced the engine and this emissions issue, it has been an extremely reliable vehicle. Everything works on it except for the Driver's side heated seat. I need to get that fixed after mine burned out this spring.  Not too shabby for a British vehicle with 112,000 miles though

Well, she is back and running smoother than ever before. $1800 in parts alone for all the O-rings, Sensors, and gaskets. Hopefully I good for a few more years of driving as they did find and fix a lot of little things I didn't even know about.

In reply to mad_machine :

In the grand scheme of things, that’s a pretty cheap car payment. 

I can only surmise that the guy who did the engine replacement just slapped it in there.. shame it cost me 40 hours for him to do that. Today the engine is quieter and smoother than ever before, "polished" is the term I would use, like a proper English vehicle that royalty would use.