i have previously posted here regarding 1999 disco one with approx. 109k miles. Miscellaneous error codes: 0300, 0304, 0308, 1177, 1179, 1187, 1316, etc. Many new parts including new o2 sensors, magna flow exhaust with cats, spark plugs, wires, Mass Air flow sensor, etc. i have checked for vacuum leaks extensively. checked fuel pressures, new fuel filter - all check ok. As stated in previous post, i noticed open loop fueling consistently after several minutes of idle even with engine warm, then will not switch back to closed loop fueling after running down road. If i stop engine, then restart closed loop fueling cycle seems to work fine. O2 sensors all show reasonable data and cycle up and down as i would expect. fuel economy is ranging from 6 mpg to 10 mpg,which i know is on the low side - but vehicle actually starts and runs pretty good.

Here is where i am at. I suspected ecm/ecu problem. took discovery to local land rover dealer thinking they would have better diagnostic tools than me. First telephone call i received from service department informed me that they needed to replace maf because data signal looked weak. I told them that both replacement maf (which was aftermarket from ebay - looked identical to original part), and the land rover maf that was in vehicle when i purchased it yielded same data. they both seemed low to me with what i had researched on internet for reasonable flow volumn in lb/min. both maf read from 0.01 lb/min at idle to approx. 0.08 - 0.1 at wot. which seems incredibly low to me.

It appears to me that ecm in vehicle is not original part - it is marked as though is came from salvage yard (i.e.. yellow ink/paint on case). i do not know entire history of the vehicle and have had run problems since i purchased it a year or so ago. ecm does appear dry and sealed though. I am thinking problem is in ecm. I have located used maf and ecm from rover cannibals in oklahoma city for reason prices, and was told dealer would need to match salvaged ecm to security system in vehicle for it to work. i am considering shipping used maf and ecm to dealer to see if these parts are the answer as i do not want to spend the several thousand dollars on new parts they are quoting me.

is there any way to check a maf sensor, or the ecm? i was told that ecm could retain "bad" data from long term that did not clear when codes were reset. i know this vehicle was run for some time with what i feel were the wrong o2 sensors before i changed them. Is there a way to "clear" data from ecm that dealer has and i don't? any thoughts appreciated.

 

i forgot to add that i know two error codes are for short and long term fuel trim being over limit. i am guessing this is related to maf readings at such low values. i will typically see both short and long term fuel trims fluctuating but seem to hover at +24.2% and -24.2%. typically short term shows +24.2%, long term at -24.2% which i am assuming are max for both.

 

Did you do a fuel leak down test? Did you replace the cat with OEM parts all long with OEM oxygen sensors. Where did you get them from. Are you sure cylinder number four isn't misfiring from a coolant problem? Did you add coolant dye to see if its getting into the cylinders?

 

I did not do fuel leak down test. I have monitored fuel pressures while running and they seemed good. Could you describe leak down test procedure?

Cats were from magnaflow. I purchased exhaust system from them from manifold to muffler with cats welded in. O2 sensors were denso. I spoke with their tech help line before purchasing to nail down correct part number from their listings.

I have not run dye through system. Truck does not seem to loose coolant though.

 

What about my low maf numbers? Could ECM be mis interpreting?

 

If you buy another ECU, buy the companion BCU from the same vehicle, no extra program needed. This assumes a D2. If a D1, no BCU. Here's pix of my D1 MAF readings at idle, with blocked radiator to make temp rise above normal. I usually run in the 180F - 187F range (180F stat).

 

I have disco series one. So it looks like you are telling me I can insert ecu from another disco series one and it should work without dealer doing some type of pairing with security system? Are there certain years of series ones that are not compatible with 1999?

My maf values at idle look similar to yours - i show 0.01 lb/min at idle, and range up to maybe 0.08 to 1.0 running at load. Why would land rover dealer have told me mine needed maf replaced for further diagnosis?. I agree that these volumn numbers for airflow look low, but if yours reads this and it's the same as mine maybe my maf is fine and not problem. Maybe it is ecu interpretation of data

Why would dealer tell me I couldn't just plug and play another ecu in this vehicle?

Thanks for your help! It seems to me that since I have tried two different maf and they each read same as yours at idle maybe I don't have a maf problem.