Here is overview-2003 Discovery:
1. Codes pulled PO171 'too lean' + PO130 bank1 circuit 1 + PO150 bank2 circuit 1 + P1171 No DTC see service manual + P1300 ignition timing adjustment terminal.
--K&N OE replacement air filter a few months back
--Oil change done 3 weeks ago with 5w40 T6 Rotella & K&N oil filter

2. I understand the 'fuses' and 'wiring' under motor to oxygen sensors need to be checked and could be an issue if fuse out or corroded.
--Will be checking the fuses today to see if any bad or wires messed with in case could be that and oxygen sensors not need to be replaced.

3. I have noticed that fluid levels have to be watched every month now and slightly fill needed every 2-4 months.

4. I changed the plugs an put iridium new in + NGK plug wires and had to remove the upper intake manifold to reach ignition coil cause top two bolts were not attached.
---Noticed afterwards some water around manifold front where the hose attachment was and could have simply been from removal of hose and re-attachment + BUT there was slight oil around this front section of where the manifold bolt goes.
--Is that abnormal? Should I check something upper section for oil issue with a gasket or anything?

5. Besides the two oxygen sensors down below is there another oxygen sensor this code for Bank1 circuit 1 or bank2 circuit 1 could be pulling from?
--The right rear bottom Oxygen Sensor I replaced a few months back.


I thank you for all your help in this matter.

 

Check the plastic nipple where the idle air control valve comes off of your intake tube. They can crack and the computer would see it as a vacuum leak as it is unmetered air. Also check your hose clamps again on the engine side of the MAF.

It may not solve the problem, but just because you were in the area it's a possibility.

 

Don't put gimick plugs into the rover. Just standard NGK's or Champions.
Anything else - well.. If you like misfires keep those plugs in.

K&N air filter - makes money for K&N selling them. But, the Land Rover
is tuned for a certain air restriction as it was built.
I would pull the K&N air filter and sell it on ebay.,

You need to put a LIVE scanner into the OBDII and see if the O2's are oscillating between 0 and .9 volts.

The front O2 sensors of bank 1 and bank 2 will do this.

The back ones just stay at a steady number when the
truck is under load and the cats are really hot.

Back will be .245 or such volts on a live scanner under load.

First, get all that K&N crap off of your intake system.
Put the truck back as it was from Rover and keep debugging.






From http://enginecodemaster.com

Engine Code: p0171

Land Rover Engine Code: P0171 = System too rich (bank 1) Multiplication injector adaptive fuelling - rich limit exceeded LH bank.

Click to Process more Land Rover Engine Codes here


Engine Code: p0130

Land Rover Engine Code: P0130 = O2 = sensor circuit malfunction (bank 1, sensor 1) Front sensor LH bank stoichiometric ratio outside operating band.

Click to Process more Land Rover Engine Codes here


Engine Code: p0150

Land Rover Engine Code: P0150 = O2 = sensor circuit malfunction (bank 2, sensor 1) Front sensor RH bank stoichiometric ratio outside operating band.

Click to Process more Land Rover Engine Codes here


Engine Code: p1171

Land Rover Engine Code: P1171 = Lean Fueling Fault

Click to Process more Land Rover Engine Codes here


Engine Code: p1300

Land Rover Engine Code: P1300 = Random/multiple cylinder misfire detected Catalyst damaging level of misfire on more than one cylinder.

Click to Process more Land Rover Engine Codes here

 

I thank you both for replies.

1. I noticed previous owner who had for most time had a zip tie on oxygen sensor plastic end where it plugs into intake plastic tube.
---Based upon what you are saying there may be an issue there as well and seen as a vaccum leak.
--Prob should replace the tube that the sensor plugs into prior to it going to air filter cover box section since is where it is zipped tied do to plastic clamps broken just in case helps adjust.

2. I didn't think i did any gimmick plugs, I simply bought the Bosh iridium plug that states fits the 03 disco.
--Should I NOT use this?
--I would have to order the NGK's from same place in town i assume I ordered the NGK plug wires.

3. Reference the KN air filter, I got discount through Advance Auto when bought it a few months back and never had issue with once put in. Actually felt a smoothness when put in.
--What best air filter you advise then if not KN?

4. I also used Rotella T6 5w40 when did last oil change with a KN oil filter.
--I understand after research that most recommend the Rotella T6, but would you guys recommend a different oil filter brand?

 

1. I would definately check that. I'm assuming you are meaning your MAF sensor and not your Oxygen Sensor. The O2 sensors are in your exhaust. As stated if you have a leak here you can get your lean code, which can in turn throw the codes for your oxygen sensors.

2. IMO I would just run the plugs you already have. The code you have relating to fuel mixture is a lean code. If you were misfiring from your plugs not igniting you would have a rich problem. Your misfires are from your lean condition.

3. The K&N filter is not causing your lean condition. The only downfall to a K&N is that it will not generally filter out smaller micron dust. This leads to premature wear of your engine over it's life. How much, I have no idea; but that's the general consensus.

Do what JFALL said though, hookup to a live scanner and watch your voltages on the front two oxygen sensors. Also you having the top intake off it may not have resealed correctly and that would result in a leak as well.

 

Hey Brandon - By idle air control valve do you mean the ones for the secondary air system?

If so, and there are cracks in the secondary air system, will they throw those sorts of codes Gromeo mentioned? I have some of the same issues and my mechanic told me is was my O2 sensor on the front right bank. Three weeks ago I replaced the other front O2 sensor. My gas mileage sucks right now!

Cheers!

 

No I was talking about this part....

*not my picture*


If you are removing and reinstalling the intake hose the area where the rubber hose connects is a weak area and can crack (area on the left of the picture).

 

Brandon -

Ahhhh okay, thanks so much. I will check that also tomorrow before installing the new O2 sensor.

I do have some of the same codes, as far as being lean and showing both front sensors being affected.

What about leaks at the throttle body connection, where the gasket sits between the two? a couple of months ago I had that off to replace the throttle body heater. I did replace the gasket with a new one, cleaned of the old one well.

Just thought of something else, could the MAF sensor cause lean codes if it was not reading properly? Two weeks ago I cleaned it with sensor cleaner so now it makes me curious if that might have affected anything other than the plastic connection which I will check.

 

That would do it as well. One way you can check is to spray carb cleaner around these parts and listen for your engine note to change. Just be careful around your exhaust or other hot parts since it's flammable. You can also listen for a hissing noise.

 

I edited my last comment but you responded before I got it on the board! Could the MAF sensor be reading incorrectly and give lean codes? I did clean this two weeks ago also.

I will check all of the connections you mentioned including my throttle body one.

Thanks so much.