I've got a 2000 Disco with 112k on it. It idles kinda strange, but will idle normal once you tap the gas, but then starts fluctuating again after about 20 seconds. One really bizarre thing, it sounds louder on one side than the other. The louder side sounds very deep, almost like a Chevy engine with modified exhaust. I might make a youtube video and post it in a bit, but just wondering what your thoughts are. I fired up our 03 Disco and it does not do it, so I know its not just me being paranoid .

It is giving the following codes:
P0171 Fuel Trim System Too Lean
P1129 Upstream oxygen sensors connected incorrectly
P1171 Oxygen Sensor System Too Lean Fault Banks A & B
P1174 Lambda control adaption fault bank 2.Last occurrence - maximum signal (oxygen sensor)

Thanks in advance!

 

IMHO - check the wiring issues for the P1129 codes, means wires to the sensors are swapped. And look to see if you have an exhaust leak on that side.

 

Here is the video as promised. Discovery Engine Sound - YouTube

 

I don't see how swapping them is possible, when looking at the O2 sensors themselves that is. Since they snake up to what appears to be the upper portion of the engine, they might have been swapped up there, idk I couldn't see. I'll dig deeper tomorrow, its almost dark out now. I couldn't see an exhaust leak, but maybe I'll seafoam it and one will show its ugly face .

 

Found this:

Possible causes
Crossed HO2S harness connectors (downstream).
Crossed HO2S wiring at the harness connectors (downstream).
Crossed HO2S wiring at the 104-pin harness connectors (downstream).


P1129 Description
The heated oxygen sensor (HO2S) monitor determines if the HO2S signal response for a fuel shift corresponds to the correct engine bank. The test fails when a response from the HO2S being tested is not indicated.


So maybe since the wires didn't jump up and move themselves, hopefully you don't have water from some kind of leak on the ecu or other connectors. And perhaps the exhaust leak is fooling the sensors, because the system tests sensor (x) and sees sensor (y) changing value at the same time (due to exhaust leak nearby) and sets this strange code.

 

Sounds like an exhaust leak where the Y pipe meets the manifold. There are 3 nuts that scew to studs. I just replaced mine. Look for black soot around the connection down there. Here are the gaskets at AB. I would start there. You need two. And you must take loose all 6 nuts to remove and slip in the new gaskets.

While down there examine your SAI pipes for a leak. Seafoaming it will reveal all.


Gasket - Exhaust Manifold To Pipe
Item: ETC4524

 

And if your bolts look like these (note leak to right of bolt, looks like black smudge), plan on soaking ahead of time in PB Blaster, and maybe a little heat from a hand torch. When at cold idle, you could feel little puffs of hot air at that joint. IR thermometer said 400 F, while rest of iron was not warmed up - yet.

Moral - a cold manifold and a "leave skin behind" one look just alike to the Mark 1 eyeball....

 

they the seafoam you may have to partly block the exhaust with a rag to get it to back up.