I have a 2001 Disco 2 with 143,000 miles. Had valve job done 10-15K ago.
Had it serviced last spring by independent Rover Repair guy, 200 miles later SES light came on. Called him back, told me he would take care of it next time came in for service. September can't get inspection because of SES light still on. Take it to local non Rover service station who runs diagnostics and says it is a misfire on Cylinder #5. Replaces. SES light goes off. Says I have to drive through cycle to retest for emissions, at almost exactly 200 miles again SES light comes on, take it back, says it is gas cap, replaces. Same thing at 200 miles. So take it back to the guy who did the valve job and service last spring. (I love the guy except he is far away.) He runs diagnostics. Replaces cylinder wire for misfire on #3. (P0303) {By the way the wires were all replaced during valve job.} Replaces O2 sensor on Bank 1 sensor 1. Replaces purge valve assembly. (P0401). Get state inspection. Runs great. 200 miles SES light comes on.
Having rebuilt engines and done major car repairs in my youth I decide I need to have more information. Which brought me to this site. Bought an, Ultra Gauge, Faults were the tandem P1171 & P1174 and P0446. I have downloaded the Rave tech manual and researched every post in every forum I could find. I am assuming that the Purge Valve Assembly he replaced was the not the CVS that seems to go with the P0446. The CVS is $225 which I would rather not replace if I do not need to. The P1171 & P1174 could be related to 02 sensors and it looks like he only replaced 1 of 4. or it could possibly be the MAF at $150. Now that you have all the information I have.... MY QUESTION.....Drum roll....... Could those vaults all be, because of using 87 grade fuel instead of 91? Always used regular, always seemed to run OK, no pinging or knocking, maybe a little rough at idle now that I have started to pay attention. I don't mind paying someone to fix it, I just don't want to have to pay to have it fixed by the process of elimination. I have read all the thoughts on the reasons for the codes, but could it be the regular gas? Thanks in advance.

 

how far away are you from a dealer? if i was you id take it to a dealer and have them diag it for an hour [80-160] than replace the part yourself. the misfire codes are most likley related to cheap fuel

 

I was checking all the hoses today and found a cracked vacuum control unit hose on the cruise control. Would that cause a vacuum leak as suggested for the P1171 and P1174 faults do you think? The tank was half full so I filled it with 93 Octane. I will run with high test for a while and see if that also stops the faults.

 

No, that is a separate vaccum system.
Do me a favor and list out all your current codes without the long story so I can maybe point you in the right directions.

 

Same ones. P1171, P1174, P0446

 

1171 and 1174 are banks 1 & 2, lean, outside the range of adaptive values the ECU can throw at it - vac leak, air leak on air hose from filter, while near there check for dirty filter. May be O2 related, but there are a lot more codes just for O2s that normally pop up.

0446 is evap canister soleniod valve test low, could be low pressure in fuel tank from bad or not tight gas cap.

 

The Northwest Overland Society list of LR Disco II Proprietary OBDII Codes below:
Which the codes say is too rich, not too lean. So what is the real meaning?

P1171
System too rich (bank 1)
Additive injector adaptive fuelling - rich limit exceeded LH bank
P1174
System too rich (bank 2)
Additive injector adaptive fuelling - rich limit exceeded RH bank

 

Here is the whole section on that set of codes from the Bosch engine management manual, for D2's MY 99 - 04. Manual version 5.2.1.

When you look at their text, it says codes P1171/2 are bank1 lean/rich, so I would take code ending in 1 to equal lean. Pages attached for your review, codes on last page.

 

Thanks you very much, Interesting that the other list has the opposite and says they are lean. Those codes were from a 99 publication and your's are 2003 so maybe they have changed them. Still not sure how to fix them but I will keep researching. I appreciate everyone's help and I see there have been a lot of people with the same codes. I am going to drive it will a full tank of premium I guess then if that doesn't work I guess I just have to start changing things. I think I will start with the MAF, I took mine out and carefully cleaned it. Still no change, then I guess I will change the O2 sensors, if that doesn't work. Then off to dealer and pay them to make educated guesses and change parts.

 

I have rec'd the same codes P1171 along with P0442, P1129 and P1300 engine runs good but has a rough intermittent idle, I purchased coil packs but haven't replaced them yet I had wires and plugs replaced not sure if this is a coil pack problem or O2 or MAF, when diagnosed it was recommended that i replace packs, wires and coil packsjust trying to make sure I fix the error...