My main goal is to past the Emission Test for my 2001 Disco SII (94K miles). Here is the history of events that have been so frustrating:
7/12/2011 (Tues)

• Emission Test (ET) – Fail – Stored Diagnostic Trouble Codes – P1171

7/14/2011 (Thrs)

• Cleaned MAF Sensor & replaced air filter – Warning light disappeared.
• 10 mins before ET warning light goes on. AutoZone confirmed codes P0102, P1171, P1884. Declined ET until noon.
• Removed battery during am – removed again at AutoZone for 15mis before testing.
• Emission Test – Rejected – Stored Diagnostic Trouble Codes – NONE

7/28/2011 – Purchased Mass Air Flow Meter – Bosch, DiscoII (ERR7171W) from BP Utah.
8/3/2011 (Weds) – Replaced MAF sensor – Warning Light disappeared.
8/4/2011 (Thrs)

• Although Warning light disappeared – Reconfirmed codes with AutoZone – P1884 (Control Transmission) appeared but tech said this has nothing to do with ET. Therefore resume ET
• Emission Test – Rejected again because 3 Systems “Not Ready” (Catalytic Conv EFF, Evaporative Control Sys, Oxygen Sensor. – Stored Diagnostic Trouble Codes – P1884

8/11/2011 – All local driving - Checked OBII codes - P1171, P1884, P1174
8/23/2011 – All local driving - Checked OBII codes - P1171 only
9/22/2011 - All local driving - Checked OBII codes - P1171 only
10/10/2011 – Purchased O2 sensors (precat) from BP of Utah
10/15/2011 – Installed O2 sensors (precat)
10/20/2011 – Service Engine Light (SEL) reappeared after 54 miles – all local/short-time driving speed was less than 40mph.
10/24/2011 – Went to Advanced Auto to check Service Engine Light - OBII code = P1171 only. Suggest to remove battery to reset board and drive highway miles to activate system.
10/25/2011 – Went to AutoZone – Reset SEL – cleared P1171 – after 10M (local driving only) SEL came back on.
10/30/2011 – Removed battery (overnight) – Reconnected batt and no SEL - Drove 70+ Highway miles (avg 65mph) – no SEL
11/2/2011 – After about 45M of local driving SEL went on again. Check OBII with Advanced Auto Parts – P1171 only.

The engine appears to be running fine and I can't identify any sort of noise/vacuum leak under the hood.

Any ideals why I still get the P1171 even after replacing the airfilter, MAF, and O2 sensors (precat only)?
Any suggestions on what to do next to fix the P1171 error so my SEL does not turn on and I can pass the emissions test?
Please advise.

 

see attached of how 1171 is generated. In a nutshell, the ECU with the sensors tries to compensate for a range of fuel delivery changes. If it can't keep things in a certain range, 1171 pops up for lean on bank 1 for instance.

The text says :

So you drove one time [and problem was really still there], then a second time and light came on.

Here's a copy with technical explanation of what is going on, which O2 sensors are involved, etc. NOT from the RAVE, but from another LR publication.

If code is telling us the truth, and the engine is actually running lean on one side, perhaps some injector cleaner solvent, like BG 44, in the tank of premium gas. New spark plugs?

 

you might have an intake gasket leak I suppose. Could also be oil in the o2 sensor connectors. What did they look like when you replaced the sensors?

These are just a couple of guesses.

 

And reasonable guess, as we have a number of posting of intake manifold bolts found finger tight....

 

Sorry for the delayed response as I was out of town. Thank you for the technical details and the Fuel System Monitoring documentation. This was very helpful and I will consider the injector cleaner solvent and/or replacement of the spark plugs.

Another issue has surfaced - My SES light started flashing and the car began to shake. This happened several times but appeared to correct itself and flashing SES stopped. In the end, there was a leak in my cooling system as the overflow tank was empty and the engines was steaming from the coolant leaking on the engine. I checked all hoses within the cooling system and could not find anything. I added Bar's Leaks liquid aluminum to stop the leak and refilled the overflow tank with Coolant. For the moment, this appears to have fixed the coolant leak temporarily. From your expertise, do you think the leak in my Cooling System is related to the P1171 code?

 

You may have cost your self a major expense, you never use Bar's Leak or the majority of other stop leak products to a Rover engine, you will starting plugging up the t/stat, radiator and heater core causing over heater issues.
Best thing you should do, is flush your coolant system as many times as necessary to get rid of that stuff.
You should have done a pressure test to find and do a proper leak repair.
As for the 1171, I understand you replaced the MAF, but because you have had the 1884 which covers 8 different issues, I would go to the Rave and read the testing procedures and verify that your MAF is within range.

 

Most stopz leakz products work by introducing some sodium silicate (water glass) in solution with a powder of the moment. That could be a clay, ground walnut shells, aluminum flakes, copper dust, carbon nano fibers, etc. In theory, this material plugs the hole in the dike, and the engine heat makes layers of glass or ceramic and you have a last forever patch. Well, that's what their ad people want you to think.

And it may have some truth to it. BUT the rest of the quart bottle of stopz leekz is still swimming around in the coolant. It will settle (by gravity) into the low spots. That will be the bottom tubes of the radiator (a cross flow design) and the four tiny holes in a D2 thermostat that sample hot coolant to make stat open when it should. Both of these conditions decrease the heat transfer capacity of the cooling system. Add old Dexcool use to the mix and you get greater degredation of the system. A jammed thermostat will really make things look good at the dealership for that new bass boat mechanic # 23 was looking at.

You should chemically flush and reverse flush cooling system and the heater core. For like 30 minutes, not 30 seconds. Refill with plain distilled water, no coolant yet. Rent or borrow pressure tester from auto parts store and pump it up to like 18- 20 PSI and hold for 30 minutes. Find leaks. You may be so lucky that it is just a hose clamp somewhere. Here is a map of the somewhere's. Once coolant system working, refill with 50/50 mix of Peak or another name brand green or yellow coolant. Don't go back to Dexcool. Coolant needs to be changed every 24 months or 30K miles. People that let coolant stay in the truck are asking for trouble.

One of the great problems of Roverdom is temp gauges that are not "lab instruments". What looks like 9:00 average may in fact be from 140 - 230 F, when you would like to be in the 190's. An after market scanner gauge, like ultra guage, can show this temp variation. Could an out of spect temperature drag the emissions off to one side and cause a code, maybe?

 

Unfortunately, I was in a bind and needed a quick temporary fix. I will plan to get the cooling system flushed out and fixed appropriately. I assume from both of your responses that the 1171 is not likely related to my cooling system leak.

Back to the 1171 issue - Why should I have to verify the MAF is within range when the Bosch device is brand new and the 1884 has not reappeared? Given both of your responses, I am starting to convince myself that the code is telling us the truth, and the engine is actually running lean on one side due to an intake gasket leak (Jafir's post) - although with the spot check of the engine, I see and hear no signs of vacuum leaks in the intake system.

 

You could spray starting fluid or another solvent around the edge of the gasket while at idle....

 

Yes - At the time, I tried spraying some starting fluid around the suspected leak on the intake gaskette but experienced no symptoms of engine choking up and could not locate any vacuum leaks.

By the way, I had put this project on hold as the Disco's been in the garage for several months now.

My main goal is to pass the emissions test so I can renew my expired license plate sticker. As soon as this is accomplished, my next step is to fix the Radiator issue.

Because I don't have the tools and resources, I am about to throw in the white towel and take it to my local land rover mechanic or a Land Rover dealership (hesitant because of the labor cost, but hoping to get an honest answer to my SEL warning)
Any advise?